The levator ani muscle; Its structure in man and its comparative relationships.код для вставкиСкачать
THE LEVATOR AN1 MUSCLE; I T S STRUCTURE I N MAN, AND I T S COMPARATIVE RELATIONSHIPS WILBUR C. SMITH Department o f Anatomy, Tulane University of Louisiana School of Medicine FIVE FIGURES F o r the last half century the levator ani muscle has claimed the attention of various writers, who have been, almost wholly, attracted to its study by the surgical importance of the general region whicli it occupies. Owing t o the difficulties which are met with in the exposure of this muscle in routine courses in anatomy, a complete understanding can be gained only by special dissections made a t the sacrifice of other structures. Recognizing this fact, many authors have made such special dissections of the perineum, but, as I point out later, abnormal female perinei have been described as normal. Artifacts due to parturition have not been recognized as such. The primary objective of the writer is t o present the comparative results of dissections of nulliparous and parous women. Secondarily, information concerning the levator ani of the male and the directions of the perineal openings in both sexes receive consideration. Lastly, there is incorporated a survey of the literature relating to the subject, not only from the standpoint of practical applications, but also including the comparative relationships of the levator ani muscle in the entire vertebrate group. I am deeply indebted to Dr. Howard Hill, of Kansas City, Missouri, for his very valuable suggestions and advice concerning the preparation of this paper, also t o Joseph Sciami and Wallace P. Sheely, both medical students in Tulane Uni175 THE ANATOMICAL RFCORD, VOI.. 26, NO. 3 OCTOBER. 1923 1‘76 WILBUR C. SMITH versity, for drawings and assistance in dissection, respectively. I am very grateful for their kindly cooperation. I n 1555 Vesalius wrote an account of the levator ani of man under the name of ‘musculus sedum attolens, ’ which description was adopted and retained until recent years. During tlie last half century, dne to the frequrnt impairment of its function in the female and to the advaricement of modern surgery, it has claimed tlie attention of various writers more than any otlier single muscle of the body. Recently it has been studied quite extensively in the lower vertebrates and gradually its divisions in man, wliicli a r e similar to the corresponding muscles in otlier vetebrates, a r e becoming more generally recognized. I have found the literature bearing upon the levator ani muscle not only voluminous, but very conflicting, particularly so in those publications dealing with the female perineum. Tlie confusion arises not only from lack of actual familiarity with the muscle, but also from failure to realize that portions of its insertion a r e very seldom the same in any two subjects and from the fact that so many different names have been given its various divisions. Wit11 the hope that it may be of general interest and of some convenience, I here include descriptions of the muscle as found in a number of the papers ~ h i c hhave been available. Paramore begins with the lowest vertebrates in wliich ail:evidence of the pelvic floor is indicated, and carries his investigation from fishes through amphibians and reptiles. I n fishes, where the pelvis is rudimentary, a pelvic diaphragm can scarcely be said to exist. A considerable advanzement of the pelvis is noted in the amphibians. I n the salamander the ileum has reached and has become attached to the rib of the single sacral vertebra by a n articulation, thus allowing a to-and-fro movement upon the spine. I n Menobranclius this upgrowth has remained incomplete, so that the pelvis is freely movable. T H E LEVATOR A N 1 MUSCLE 177 I n both Menobranchus and the salamander evolutionary advance trended toward the fixation of the pelvis to the vertebrae, although this is completely attained only in the latter. This fixation is associated with progressively greater variations of internal pressure, owing to increase in the general bodily activity of the higher forms. In reptiles the sacral vertebrae are present and connecte,tl with each other by fibrous tissue. The pelvis is completed inferiorly by the juncture of the pubic and the ischial bones, which may form a median syniphysis. I n Iguana the caudopelvic muscles are very well developed. Instead of a single caudo-pelvic muscle, as in some other lower vertebrates, two a r e found on each side. The larger and the most superficial a r e situated on each side of the cloaca, dorsal to which their medial borders a r e in apposition. The recti, transversalis, and the two oblique muscles are present. A comparison of the anatomical conditions in reptiles, the Iguana, with those in the salamander, coupled with a consideration of their habits and mode of life, indicates that the advance in structure is due to a n increase in the general activity and to the change in respiration. The crocodile presents more advanced structures than the Iguana, although the caudo-pelvic muscles are not so greatly developed. Here the pelvis is ankylosed to the spine, a circumstance which is coincident with diminished utility of this musculature. I n the European tortoise a caudo-pelvic muscle (pubo-coccygeus) is present on each side, together with the sacro-coccygeus. The evolutionary series, through the fishes, the amphibians and the reptiles, suggest that the muscles occluding the pelvic outlet exist f o r the most part wholly for a pressure effect. Lartschneider, who extended his investigation through the order of Mammals, says, “the levator ani in man has originated by the fusion of two separate paired tail flexor muscles like those of the short and the long-tailed apes and of the dog,” namely, the pubo-coccygeus and the ilio-coccygeus, both of which can be readily recognized. 178 WILBUR C. SMITH Within every order of mammals the pelvic muscles of the different species show certain interesting relationships. Certain peculiarities occurring in the arrangements and development of the pelvic muscles in any species a r e present in the case of all other species of the same order. Variations from this a r e due to the retrogression of the tail part of the long vertebral column characteristic of such mammals as the Edentata (ant-eaters). The more primitive members of any order of mammals show a greater separation of the pubococcygeus and the ilio-coccygeus from each other than is seen in the less primitive. To begin with, the great skin muscle (cutaneus maximus) must be clearly considered. I n tlie case of the rabbit this muscle forms a large circular sack, situated immediately under the skin and enveloping nearly the whole of the body. The fiber-fasiculi of this muscular sac extend into the caudal end of the body, from the lumbar and the abdominal region, over the two nates to the median line of the dorsal surface of the tail, where they insert themselves almost quite up t o the tail tip. Some fibers issue from this great skin muscle, forming a broad, rather strong, ligament-like muscle which runs forward past the rectum to become attached to the corpuscavernosum penis, almost, if not quite, to the tip of the latter. These fibers represent the pubo-coccygeus muscle of the rabbit. Likewise, the bulbo-cavernosus, the ischio-cavernosus, and the external sphincter have the same origin. The dissection of the pelvic cavity of the rabbit, from within outward, shows that the obturator internus lies on both sides of tlie rectum throughout its entire course in the pelvic cavity. I n the higher mammals the greater part of the cutaneus maximus draws itself more and more from the caudal half of the body toward the head, until in man it is only represented by the platysma and some of the skin muscles of the face. On the other hand, those parts which the great skin muscle sends off to the end of the alimentary tract and to the external genital apparatus remain in the higher vertebrates as muscles THE LEVATOR AN1 BIUSCLE 179 apparently quite foreign t o it and independent even after disappearance of the chief bnlk of the parent muscle, namtly, the pubo-coccygeus, sphincter ani, bulbo- and ischio-cavernosus. I n the ant-bear (Myrmecophaga tamandua) the pubo-coccygeus arises from the body and the descending ramus of the pubis and runs dorsocaudally t o gain its insertion upon the ventral surface of the first coccygeal vertebra. I n the Marsupialia, Carnivora, Prosimiae, and the Primates, the pubococcygeus takes origin a t the linea terminalis of the pelvic outlet in the region of its ventral third. I n certain Primates (Macacus maurus, Cynocephalus mormon, Troglodytes niger ) the attachment of the pubo-coccygeus moves down to the lateral wall of the small pelvis until eventually it reaches that point of attachment common to the orang-outang and man. I n these the dorsal end of this musele has completely separated from its equivalent in the rabbit, and in the case of the longtailed Edentata, Marsupialia, Carnivora, Prosimiae, and Primates is inserted to the lateral border and the median and ventral surfaces of the tail near the last coccygeal vertebra. I n Edentata, Marsupialia, Carnivora, Prosimiae, and tailed Primates, the pubo-coccygeus is a separate muscle, which arises from the back of the 0 s pubis and inserts itself upon the ventral surface of the tail root. These muscles are separated by a large cleft for the external sphincter, the bulbo- and ischio-cavernosus. I n the muscles of the pelvic outlet of the Ungulata (roe and horse), one encounters a powerful external sphincter, which passes ventrally to the bulbo-cavernosus, and from the fusion of these fiber-fasciculi pass t o the root of the penis. On the lateral side of this mass there arises a broad Iigament-like muscle which fastens itself to the lateral wall of the true pelvis. This ligament-like muscle corresponds to the pubococcygeus of the Edentata, Marsupialia, Carnivora, Prosimiae, and the Primates, except that a few fasciculi run into the fascia of the tail and that its origin extends farther dor- 180 WILBUR C. SMITH sally. It functions as a suspensory muscle of the rectum. The pelvic inclination in the Ungulata and the attachments of the muscles back as f a r as the coccygeus allow no other function. I n the Ungulata those muscles which have split themselves off from the cutaneus maximus a r e situated around the end of the intestinal tract and the external genitalia. I n the Edentata, Marsupialia, Carnivora, Prosimiae, a ligament-like band separates itself on both sides as the pubo-coccygeus. From this muscular mass the band passes from the pelvic outlet along the lateral pelvic wall into the pelvic cavity and functions as a flexor of the tail root. While the pubo-coccygeus of man, as of other mammals, must be considered as having been derived from the cutaneus maximus, the ilio-coccygeus belongs to that group of skeletal muscles found on the ventral surface of the tail part of the vertebral column. I n the Ungulata one finds powerfully developed skeletal muscles on the ventral surface of the sacrum. These act as flexors, and vary correspondingly with the development of the tail. There result numerous variations, of which the horse and roe show opposite extremes. Laterally the caudal flexors reach the lateral pelvic wall and continue to broaden. From the ischium, they move u p t o the ileum, and finally separate themselves from the chief mass into independent muscles, the ilio-coccygei. This is beautifully demonstrated in the shorttailed Edentata. I n the long-tailed Edentata t h e e flexors a r e found on each side, lateral, medial, and intermediate. These run side by side to gain their insertion into the ventral surface of the tail nearly as far a s the tip. I n the Marsupialia the intermediate flexor has withdrawn from the caudal fourth of the tail, but in the Carnivora, Prosimiae, and the Primates, when the vertebral column retrogrades, the lateral and the medial flexors disappear leaving the ilio-coccygeus much the more prominent. I n man the ilio-coccygeus forms a part of the pelvic diaphragm, and the flexor caudae medialis and lateralis, which THE LEVATOR A N 1 MUSCLE 181 a r e so prominent in the lower vertebrates, remain as fiberfasciculi, the sacro-coccygei anteriores. The pubo-coccygeus, i n the Carnivora a separate muscle, is a flexor of the tail root, which was a t one time a part of the cut aneus maximus. I n short-tailed Primates the flexores caudae medialis and lateralis have atrophied to thin fibrous bands, leaving the iliococcygeus to predominate. The pubo-coccygeus in its dorsal part becomes tendinous, and, on the point of casting off its intimate relations to the tail part of the vertebral column, it separates itself into fibers which for the greater part pass to the median line to blend with those of the opposite side. The tail flexor muscles, grouped in pairs, join or fuse to form the pelvic diaphragm and close the pelvic cavity at its outlet. Now, in the short-tailed Primates, as already mentioned, these muscles gradually lose their relation to the tail part of the vertebral column and unite by means of tendinous portions to the coccygeal vertebrae and with the muscle of the opposite side. They form an unpaired muscle, stretched out in a transverse direction and closing the pelvic outlet. In the chimpanzee, the retrogression of the tail part of the vertebral column has reached its highest degree. The caudal end of the tail approaches the pelvic outlet. The flexor muscles, which previously a r e grouped in pairs, now unite to form one, the diaphragm of the pelvis. The pubo-coccygeus of the chimpanzee is a ligament-like muscle and arises on each side by means of tendon fibers from the line& terminalis, and passes with its medial border next to the rectum, behind which the two muscles unite and gain attachment to the ventral surface of the coccyx and the last sacral vertebra. The ilio-coccygeus has become altered with the concurrent reduction of the tail. It still arises on both sides of the pelvic cavi t y ; i t is reduced to a delicate thin muscle whose fibers extend fan-like from their origin, terminating in a fibrous tendon, the ventral border of which rests upon the pubo-coccygeus. The coccygeus is in its greatest part transformed into a ten- 182 WILBUR C. SMITH don, so that now one finds that, after the atrophy of the visible tail muscles, which were once flexors of the tail, the pubococcygeus and the ilio-coccygeus join together t o form an unpaired muscular sheath, which stretches itself out in the bony frame of the pelvic outlet, being perforated by the rectum, the vagina, and the urethra. Going further in the series of the anthropoids and comparing the pelvic diaphragm of the chimpanzee with that of the orang-outang, one finds a gap a s great as that between the chimpanzee and man. The pelvic diaphragm of the orangontang is nearly of the same grade of development as that of man. Kohlman writes regarding the levator-ani of the Chimpanzee: “The dorsal portion which in tailed apes is present in great strength is transformed into a fascia. Of the levator there is still only the ventral and lateral original portion.” Rudolf Pick states that the levator-ani of the orangoutang is much extended, especially the posterior fasciculi and the ischio-coccygeus, but in essentials does not differ from that of man. Lartschneider has called attention t o the bearing of the upright position upon the origin of a pelvic floor. He regards its development as a natural consequence of changed position of the body. The pelvic outlet of man, by virtue of his upright position, is directed almost downward ; the diaphragm a t the base stretches itself out, hence closing the outlet on which the pelvic organs in part rest. The dorsal part of the pelvic floor in the chimpanzee consists of the fibrous ilio-coccygeus, which, due t o the position of the pelvis, forms a part of pelvic roof. This is in contrast to the condition in man where it forms a visceral support in the pelvic floor. The levatores consist of two portions, the ilio-coccygeus and the pubo-coccygeus. The f ormer belongs to the vertebral column musculature, being the remnant of the flexor tail muscles (flexor caudae medialis and lateralis), or sacro-coccygeus of man. The pubo-coccygeus of man is traced back to the great skin muscle, the cutaneus maximus. THE LEVATOR A N 1 MUSCLE 183 Lartschneider suggests that it would be advisable to describe the levator ani as follows: “It is subdivided into two portions, portio pubica and portio iliaca. The portio pubica arises as a thin muscular layer on both sides of the symphysis pubis, extending outward as far as the entrance inta the obturator canal. The fibers a r e directed backward at the sides of the rectum and converge behind it where the medial fibers cross and form a loop. The fibers which, on both sides, arise more laterally from the pubis are directed toward the coccyx and a r e inserted by means of a common tendinous aponeurosis to the second, third, and fourth coccygeal vertebra. Between the coccyx and the tendinous aponeurosis there exists a space exactly in the midline which is filled partly with f a t t y tissue and which serves as a passage for the nerves, venous plexuses and the end of the middle sacral artery. “The portio iliaca arises in the continuation of the line of the origin of the pubic portion as f a r as the ischial spine, to a greater extent from the obturator fascia and to a smaller extent behind this from the medial surface of the ischium. The most posterior fibers a r e inserted into the lateral border of the last coccygeal vertebra, whilst the fibers in front of these a r e attached to the raphh, which extends from the tip of the coccyx to the a ~ i u s . By this raphd the portio iliaca of one side is joined with that of the opposite side to form a muscular plate stretched obliquely behind the portio pubica” (literal translation), Thompson states that Lartschneider ’s views of the levator have not been adopted by succeeding writers. As noted above, the latter applies the terms portio pubica and portio iliaca to the levator divisions in man and other mammals. Thompson asserts that, since the ilio-coccygeus in man represents the ventral fibers only, the pubo-coccygeus includes the puborectalis. The portio pubica of the levator ani is not exactly the pubo-coccygeus in mammals generally. Thompson states also that neither the ilio-coccygeus nor the pubo-coccygeus are present i n the Ungulata, and that the view of Lartschneider, concerning the origin of the pubo-coccygeus 184 WILBUR C. SMITH from the cutaneus maximus was based upon observations confined to the rabbit. It appears that the superficial sphincter of the rabbit was mistaken by Lartschneider for the pubococcygeus. Holl likewise makes this interpretation, and in it also states that Lartschneider 's conclusions are incorrect. I n the camel there are two muscles which arise from the internal surface of the ischium, one close to the spine ancl one, more ventral, close to the obturator foramen. The latter passes along the lateral aspect of the rectum to terminate in short tendinous fibers in its walls near the anus, none being attached to the caudal vertebrae. HoH calls the dorsal muscle the ilio-coccygeus and the ventral muscle the pubo-coccygeus, while Thompson and Lartschneider hold that the dorsal niuscle is the ischio-coccygeus and the ventral the pubo-coccygeus. Lartschneider thinks that the ventral muscle is the pubo-coccygeus of man. Thompson raises the question as to which of the flexor tail muscles it corresponds-the ilio-coccygeus or the pubo-coccygeus, or both. Paulet (as quoted by Hogge), writing on comparative anatomy of the perineum, stated that the ischio-anal muscle in the stag is homologous with the levator ani of man, but that it differs from i t in form. H e regards the muscIe as corresponding only to a limited part of the levator ani, to that p a r t which remains if the fibers from the pubic ancl obturator fascia be removed. Hogge, i n investigating the muscles of the perineum, used human embryonic material, but his method of investigation was that of serial sections, and he did not study the adult anatomy, to which his method could not be applied. Hogge points out that it is well, however, to remember that in the foetus at term and in the young child the intra-pelvic organs do not occupy exactly the same position as in the adult. F o r example, the anus is more superficially placed in the foetus. The bladder in the foetus and in the child lies well above the superior border of the symphysis pubis. It is more vertically placed in the child, not reaching the pelvis until about the age of eight years. THE LEVATOR A N 1 MUSCLE 185 P e t e r Thompson, who perhaps has done more work on the muscle than any of the past o r present generation, described it ( ,OO) as follows : “The levator ani in the human subjects arises along a n interrupted line from the back of the body of the pubis, from the pelvic fascia on the side wall of the pelvis and from the spine of the ischium; its fibers a r e inserted into the coccyx and the ano-coccygeal raphe, while a few pass to the central point of the perineum. I t is clear, therefore, that most of the fibers at their insertion a r e post anal. “Ilio-coccygeus arises from the pelvic fascia and from the inner aspect of the spine of the ischium. I t s attachment to the pelvic fascia is along a curved line whose concavity is directed upward. The line has a varying relation to the side wall of the pelvis ; in some cases it is situated almost as high as the obturator canal, and in other cases considerably below it. Posteriorly the origin of the ilio-coccygeus extends as far as the margin of the great sacro-sciatic notch, whilst anteriorly its limit is not always easy to determine. It reaches almost as f a r a s the commencement of the obturator canal, and f o r those cases in which there is no clear separation between the ilio-coccygeus and the pubo-coccygeus. The fibers a r e directed downward, backward and inward to the coccygeal vertebrae. They a r e inserted from behind forward into the lateral margin of the last two of the coccyx, into the tip of the coccyx to the posterior margin of the same. A t their insertion the fibers a r e not all on the same plane, but have a series of layers superimposed upon each other, the upper layer consisting of fibers from the posterior end of the muscle. The middle layer consists of fibers from the muscle of both sides which decussate without forming a raphe, whilst the most inferior forms a tendinous raphe in which most of the fibers terminate. “The pubo-coccygeus invariably arises from some part of the pubis: in man from the back of the body of the pubis along a n oblique line which extends from the lowest limit of the symphysis upward and outward toward the obturator canal. Also from the obturator fascia for a limited extent along a line continued forward from the origin of the iliococcygeus. The limits of the two muscles at this point arv often difficult to define. The fibers form a flat band about one 186 WILBUR C. SMITH inch wide, thick on its medial border, thin where it overlaps the ilio-coccygeus, it is directed backward almost horizontally along the side of the canal toward the coccyx and sacrum to which it obtains attachment. Between the tip of the coccyx and the anus the two pubo-coccygeus come together and form a thick fibro-muscular layer lying on the raphe formed by the ilio-coccygeus, nearly all of the pubic fibers pass backward to the vertebral column. They are joined behind the rectum by the corresponding fibers of the opposite side and becoming tendinous form a thick aponeurosis which is continued upward in front of the coccyx and divided into two lateral por tions which have been named the ligamenta sacro-coccygea anteriora and a r e fastened to the lower part of the sacrwn and the upper p a r t of the coccyx; a few of the pubic fibers pass inward to the central point of the perineum, descend in close contact to the walls of the rectum and terminate in +lip external sphincter ani and the skin of the anus. The obturator fibers form the outer border of the muscle and becoming tendinous join with the ligarnentum sacro-coccygeum anterius. A few decussate in the midline and lie on the upper aspect of the thick tendinous aponcurosis which constitutes the chief insertion of the pubo-coccygeus. “Pubo-rectalis: arises from the back of the lowest part of the synipliysis pubis under cover of the pubo-coccygeus, from the upper layer of the triangular ligament and from the pubis immediately below the symphysis. From this origin the fibers pass around the lower p a r t of the rectum and, meeting with thcl fibers of the opposite side, form a strong loop, or girdle which slings the rectum u p to the symphysis.” Holl refers to this division as the best-developed muscle of the perineum. Henle, in describing the pelvic diaphragm, considers this the only muscle of the levator ani. Thompson states that the ilio-coccygeus is a degenerated muscle in man. Paramore replies to this statement with the observation: “ I n the tailed apes the levator attains a thickness of 5 mm.; in anthropoids it is thin and almost transparent,” and he asks, if it is a degenerated and unnecessary muscle, why is it present in man and absent in the mare and the cow. Furthermore, if atrophy has commenced in certain anthropoids, why has it not reached a higher development in THE LEVATOR A N 1 MUSCLE 187 m a n ? Holl states that i n the dog and the cat the pelvic diaphragm is composed of the pubo- and the ilio-coccygeus. I n tailless apes one finds a n abductor caudae, but the ilio-coccygeus is lacking. Berry Hart published his own researches on the anatomy of the female pelvic floor, followed by a more extensive work relating to the topographical and sectional anatomy of the female pelvis. Berry H a r t and Dr. Henry Coe, in speaking of the pelvic floor, state that it includes both the bladder and the rectum. It seems, in looking over the literature published since this time, that many of the authors make mention of this statement, and all offer the same objection, namely, that if the bladder is a p a r t of the pelvic diaphragm, it at times rises up to the umbilicus in distention. The writer is confident that both Coe and H a r t had in mind just that portion of the bladder which is in direct contact with the levator ani. Meckel considers the levator as consisting of one undivided muscle in the male, but divides that of the female into two parts. Testut divides the insertion of the levator ani into three sets of fibers : post-rectal, lateral rectal, and pre-rectal, claiming with Cruveilhier and Thompson that the lateral rectal fibers a r e lost in the longitudinal muscular fibers of the wall of the rectum itself, while Kalischer considers the levator as one muscle and identifies three sets of fibers in it, pre-rectal, rectal and post-rectal. Savage, to whom we a r e greatly indebted for his beautiful work on the female perineum, divides the levator into the pubo-coccygeus and the obturator-coccygeus, and Symington and Raney accept the divisions as named by Savage. Cruveilhier and others consider that the anal sphincter and the levator ani act a s one muscle; they separate its fibers into vesico-rectal fibers, pre-coccygeaI, coccygeal and sacral fibers. Rour (as quoted by Hogge) treats the levator ani as consisting of a superficial and a deep part, the former including only about one-half of the generally accepted insertion; the latter he states is the levator proper. In a diagram he shows the deep fibers passing in front of the rectum. Poirier 188 WILBUR C!. SMITH and Cliarpy separate the levator into two portions, a superficial external part and a deep portion, internal or elevating. According to the investigations of Sqppey, Kahbrausch, Luschka, Lesshaft ( a s quoted by Hogge) and Meriel, the levator ani is made up of the anterior, middle, and posterior bundle of fibers. Holmes describes the levator as a muscle of continuous origin, but defines two insertions. H e suggests that the name, levator ani, should be changed to tensor peronei. Dickinson speaks of the levator ani as a horse-shoe muscle, and for its insertion, like Luschka, describes three sets of fibers, and Robinson accepts Dickinson as to this shape and describes an origin from three separate points. Doran describes the levator a s consisting of two divisions, the pubococcygeus and the ilio-coccygeus, but in the specimen he describes the ilio-coccygeus is not such as one finds in a normal subject. Harrison does not consider the levator ani as taking any part in the formation of the perineum. Browning asserts that in his investigations of the male and the female perineum of tlie lower animals and of man, he invariably found that the levator ani is the better developed in the male. This can readily be explained from the fact that in the male the intraabdominal pressure is greater. H e divides it into the pubococcygeus, fibers coming from the ischial spine, and intervening fibers. Eckley divides the insertion of the levator ani into three sets of fibers, but gives them no name. Goffe describes tlie levator ani as one continuous muscle, stating that it arises from the entire circumference of the bong pelvis and is inserted into the tendinous center known as the perineal raph6. Marcey claims that the levator ani is inseparably blended with the sphincter ani. H e treats it as one muscle, stating that the use of names employed by modern text-books leads to confusion. Derry, Elliott Smith, and Keith speak of the levator as consisting of two portions, namely, the pubococcygeus and the ilio-coccygeus; but Derry says that the white line so commonly spoken of is composed of the tendinous fibers of the levator ani muscle itself. Rtuddiford separ- THE LEVATOR AN1 MUSCLE 189 ates tlie inserting fibers into three sets, as Sappey, Kahbrauscli, Luschka, Lesshaft and Meriel have done, namely, the anterior, the middle, and the posterior. But Studdifortl states that the fibers running behind the vagina a r e composed almost entirely of involuntary muscle, as proved by the microscope. He has taken for examination fibers of the internal sphincter ani, or part of the rectal mall. I can find on microscopic examination no evidence of involuntary muscle. Harrison bakes up the levator ani into three sets of fibers, the pubo-coccygeus, the ilio-coccygeus, and the pubo-rectalis. In 1923, Frank, i11 his description of the anatomy of the pelvis, speaks of the muscles thus : “The pelvic outlet is closed by a thin but strong musculo-f ascial diaphragm, called the levator plate, cornposed of the two levatores ani and the two coccygeus muscles. ) ’ Holl is worthy of special mention. He divides the levator aiii into the ilio-coccygeus, pubo-coccygeus, and pubo-rectalis, the same as Harrison has done. H e had previously suggested that the name, levator ani, be discontinued. A summary of his findings is given below. Zlio-coccygeus. This muscle is found well developed in many mammals, but often in man reduced to fibrous tissue. It runs backward to gain insertion into the raphh between tlie anus and the coccyx. I find that this muscle is the coccygeus as described by Henle and that it is the iliac portion of the levator of Kohlman. Pztbo-coccggeus. This consists of two layers, superior and inferior. The inferior layer arises from tlie entire surface of the deep layer of the urogenital trigone and from the internal surface of the descending ramus of the pubis and the neighboring part of the obturator fascia. The superior layer forms a sort of gutter, opened externally and posteriorly, in which the inferior layer is received, and it is attached to the tip of the coccyx. The inferior layer becomes fibro-elastic and becomes attached to the fibers of insertion of the pubococcygeus. A deep layer of the superior layer surrounds the 190 WILBUR C. SMITH intestine like a strap. The most internal fibers of this layer pass i n different directions to gain their insertion. Some descend to the central point of the perineum and go to form a large p a r t of the superficial perineal muscle, or a r e continued into the external sphincter, almost invariably some of the fibers which remain on the same side going into the external sphincter. Other fibers pass around the posterior border of the urogenital diaphragm to terminate in the bulbo-cavernosus, or become attached to the inferior layer of the urogenital diaphragm. Still others find their way to the anterior and the levator surface of the rectum, become tendinous and, together with the smooth longitudinal fibers, find their way to the skin of the perineum in the neighborhood of the anus, or terminate in the central point of the perineum. Pubo-rectalis. This arises from the posterior surface of the body of the pubis, along a line which extends from the inferior border of the synchondrosis toward the obturator canal, and, further from the obturator fascia, follows a line toward the ischial spine to the fibers of the ilio-coccygeus. From this point of origin the fibers are directed backward in two layers, an internal and a n external. The external layer arises from the obturator fascia. The two layers together pass f o r the most part behind the rectum, forming with the fibers of the opposite side a layer which is muscular in front and tendinous behind, and dorsally extend by means of slips to the last sacral and the first coccygeal vertebra. It is between these two prolongations that the middle sacral artery passes. The fibers passing beliind the rectum have no connection with its wall. Some of the fibers coming from the back of the pubis pass in front of the rectum, some to the sides and others posteriorly. I n front and on the sides of the rectum the connective tissue unites the latter to the pubo-coccygeus muscle, this fibro-elastic tissue emerges from the connective tissue of the pubo-coccygeus muscle itself. Some of this fibro-elastic tissue spreads out between the fasciculi of the external sphincter and finally terminates in the integument of the perineum with the longitudinal fasciculi of the rectum. THE LEVATOR AN1 MUSCLE 191 I find that this pubo-rectalis of Holl is the levator of Henle and the pubic portions of the levator of Lartschneider, and that also Holl describes as the pubo-coccygeus that part of the origin of the muscle which, according to other authors, makes up the pubo-rectalis, and vice versa. From our modern text-books i n gross anatomy the following accounts may be mentioned: The original Gray describes the levator ani as one muscle, but divides the fibers of insertion into three different sets, namely, the anterior, the middle, and the posterior, as has been done by Studdiford, Sappey, Kahbrausch, Luschka, Lesshaft, and Meriel. This description has been accepted in toto by Spitzka, Howden, and Lewis, and Quain and Gerrish divide them similarly. Piersol and Cunningham make no divisions of the levator, bat describe it a s a single muscle. Bardeen, in Morris’ Anatomy, divides the levator ani into three sets of fibers as found in the lower vertebrates, the pubo-coccygeus, the ilio-coccygeus, and the pubo-rectalis, but lie labels the pubo-rectalis as the pubococcygeus in his diagram. Fr o m the above mass of literature one can readily see the problem that confronts us. There is no single muscle in the entire human anatomy which has as much significance to the surgeon, the gynecologist, the obstetrician, or the general practitioner as the levator ani; certainly none whose attachments and functions should be better understood. A great deal of the literature has been contributed by these men. I include the practitioner for the simple reason that it is he who is usually present when partial impairment of function occurs. I t is he who so often innocently and ignorantly attempts to make repair by bringing togclther whatever tissue may lie in front of his needle in such a way as to get the apposition and union of the skin, but who so often fails entirely to close the rupture of tlie fibers of the muscle whicli is the real injury, leaving their torn ends to retract and the interval between to become a weakening point of the pelvic floor. Not only is tlie practitioner guilty of this offense, but also is that surgeon who undertakes the THI hhATO\lIChl KI CORI), \ 0 1 . 2 6 , 50. 3 192 WILBTTR C . SMITH repair from surgical knowledge only, without a sufficient conception of the insertion of the various fibers or the function of the muscle itself. I believe that in every case of confinement, without exception, the function of the levator ani is impaired Fig. 1 Showing perineum of a girl of about twelve years of age, viewed from below. All of the superficial muscles, with the exception of the external sphincter ani, have been removed. The lerator a n i muscle from this view shows principally the pubo-rectalis and the ilio-coccygeus. The former can be seen as a thick band of fibers, thc most mesial of which surround the vagina, forming its true sphincter. The fibers behind the pubo-rectalis constitute the ilio-coccygeus. The most posterior muscle in the space is the coccygeus, represented by a small but distinct bundle of fibers. The vagina and the anus a r e seen t o be opening at right angles t o each other. It is t o b e noted especially t h a t the anus is directed almost straight backward. T H E LEVATOR AN1 MUSCLE 193 to a greater or less extent by stretching or tearing some of its fibers. Often the fibers a r e ruptured, though the skin and mucous membrane remain intact. I have always tried to impart to the student that the rupturing of a muscle o r any part of its fibers results quite similarly to the retraction of rubber after rupture when placed on tension. Fig. 2 Shows the levator a n i muscle from above, adult male. The most anterior and medial fibers, which a r e on a lower plane, belong t o the pubo-rect a l k The most prominent muscle, the pubo-coccygeus, which resembles a V and embraces the anus, extends back to the t i p of the coccyx. Lateral t o this and lying in a lower plane, t h e ilio-coeeygeal fasciculi a r e disposed at a n obtuse angle with the former. The coccygeus occupies the remainder of the pelvic floor. 194 WILBUR C . SMITH One finds it refreshing to read the descriptions of this muscle in the scientific publications of Savage, Thompson, Hogge, Hart, Lartschneider, and Holl, authors who have equal knowledge in human and comparative anatomy, but it seems curious to note that in all the literature to which I have had access (save perhaps the atlas of Hart) not a single illustration shows the openings of the perineum in tlieir correct anatomical position. This lack is especially true for tlie anus. Tlie anal opening, according to my own observations, points hack at an angle of nearly 80". Many authors have stated that tlic vagina and the anus lie at riglit angles to one another, which is quite true, but they make no reference as to horn tlie openings point. Their diagrams sliow tlie openings of tlie anus pointing almost straight down in the standing POsition, o r sometimes back a t an angle of about 15". I believe H a r t recognized the correct condition, but, as is stated by inany others, he shows the anal opening back toward tlie point of the coccyx, necessarily omitting the levator ani muscle between the two. While practically all authors, with a few exceptions, agree as to the general origin o f tlie levator ani, it is its insertion and its function which have given rise to so much confusion in descriptions and controversy. I have found (figs. 1 to 4) that in both tlie male and feinalc, by careful dissection of many subjects, tlie levator ani is composed of three distinct sets or fibers, both at its origin and at its insertion, namely, tlie pubo-coccygeus, ilio-coccygeus anti the pubo-rectalis, as described by Bardeen. The pubo-coccygeus, best seen from above (fig. 2 ) , springs from the pclvic surface o f the body of the pubis and the superior mmi, back as far as the attacliment of the ilio-coccyg ~ u s . It is a thin, strap-like muscle, ~vliicli rests upon tlie npper surface of the pubo-rrctalis and tlie ilio-coccygeus. From their origin its buntlles pass bacliward and medialmard, a few fibers from tlie medial border passing in front of the rectum (fig. 2 ) to blend with tliose of tlie opposite side and m-itli tlie sphincter ani. Lateral t o these, a band of ahout 1% THE LEVATOR A N 1 MUSCLE 195 em. in breadth surrounds the rectum like a collar. The major portion of the muscle extends backward, uniting with its fellow across the mid-line between the anus and the coccyx, but some fibers continue backwards to become attached to the lower three or four coccygeal vertebrae. Fig. 3 Inferior vicw of the perineum of a nullipara in which all the superficial iiiuscles have been removed with the exception of the external sphincter ani. S1ioi.c.s the openings of the vagina and anus, the fibers of the pubo-rectalis, iliococcygeus, and coccygeus muscles. Compare with figure 1, noting particularly clifferences in laxity and direction of levator fasciculi. The conditions exhibited may be attributed to mechanical factors other than gestation and labor-intercourse, for example. 1'36 WILBUR C. SMITH The ilio-coccygeus (figs. I to 4 ) , the broadest, thinnest, and the most degenerated division of the levator ani, takes its origin from the pelvic surface of the ischial spine and from the arcuate line, o r white line. This line consists of fascia extending obliquely upward a s f a r as the superior ramus of the pubis, in the region of the obturator canal. F r o m this latter origin, its bundles run almost transversely medialward, most of them joining the opposite fellow between the anus and coccyx. Some, by means of a n aponeurosis, become attached to tlie lower coccygeal vertebrae. The pubo-rectalis, tlie most massive p a r t of the levator m i , takes its origin from the lateral edge of the pelvic surface of tlie body of the pubis, from the pelvic surface of the proximal p a r t of the descending pubic rami, and from tlie upper layer of the urogenital trigone. The fibers pass almost directly backward, close to tlie side of the vagina, to gain their insertions. Upon reaching the posterior part of the vagina, a band departs from the medial margin of the muscle. The terrnination of this band is traceable to its fellow of tlie opposite side and to the opposite external sphincter ani. Froin the lattor termination, a few fibers may be further distinguished, being attached by means of elastic tissue into tlie neighboring skin. The bulk of the muscle passes still farther backward along the lateral surface of the external sphincter ani to fuse with the corresponding opposite muscle between the anus and tlie coccyx, but a small contribution continues from it to the coccyx, either as muscle fibers o r aponeurosis (fig 4). On passing along tlie lateral side of the sphincter ani, some of the fibers become lost in the fibers of the sphincter itself, and some of then1 terminate in elastic tissue, which ends in the skin around the anus. The proportion of fibers running to the skin amount to very little. However, fibers from both this arid the pubo-coccygeus, as noted above, terminate in the skin. I must agree with most of the authors stating that no fibers of the levator terminate in the rectal or vaginal walls proper. T H E LEVATOR A R I MUSCLE 197 Furthermore, T am convinced that tlie pubo-rectalis is tlie true vaginal sphincter. Aware of the difficulty in obtaining a nullipara in tlie dissecting room, I have often been concerned with the question of whetlier the descriptions of the levator ani muscle have not orignated from subjects like that illustrated in figure 5, a multipara. Doubtless some descriptions deal with multiparae Fig. 4 Lateral aspect of the levator ani, adult male. The fasciculi of the pubo-rectalis and ilio-coecygeus can be traced from origin to insertion. 198 WILBUR C . S M I T H in wliich tlie skin and mucous membrane had never been torn, o r possibly subjects in which repair had been made sometimi. prior to death. These, to the naked eye, could easily be mistaken f o r normal perinea. Such material might account for the variations in tlie numerous descriptions of this muscle, especially a s regards the insertion of its fibers. I have included a drawing from such a multipara (fig. 5) to illustrate this possible explanation of these variations. Dissections of the various perinea of parous women often suggest that the fibers of the right levator may differ somewhat from those of the left. The arching of the levator fibers often appear more pronounced in parous females than in iiulliprae. On the right side they may form a wider curve than on the left. This may be accounted for from tlie fact that in 90 per cent of all cases of labor there is either a LOA or n ROP position of the Iiclacl. This means that the posterior aspect of the head of the child must come to press upon tlie right side of the pelvic floor. l’lic right side of the muscle mill naturally become more stretched and is more liable to tear tliaii the left side. My experience with tlie levator ani lias taught me that even in the nullipara there occurs a certain amount of variation of its fibers. I n some subjects the fibers passing beliincl the vagina seem t o comprise a rather large bundle and in others they seem greatly reduced. I n some specimens tliere appears to be a greater proportion of fibers termiiiatiiig in elastic tissue which runs to tlie skin tlian in others. I n sonic cases one finds muscular fibers continuing back to the coccyx and in others they appear to terminate in an aponeurosis wliicli gains its attachments to the coccyx. Tlie ilio-coccygeus seldom appears the same in any two subjects. I n some it is fairly well developed and in others quite thin and aponeurotic. This latter condition is invariably found in old subjects o r in those in which laceration has occurred, and it is responsible, no doubt, f o r impaired functions of the pelvic diapliragm. Fig. .5 Lateral view of the levator a n i of R parous female, sliowing a laceration e\tending to anterior margin of anal opening, including fillers of botli levator a n i and external sphincter ani. The origin of the fibers of both the puborertalis and the ilio-coccygens a r e distinctly indicated, the former terminating bluntly in the side of the vagina-a condition which is caused by ruptures of the fibers hetveen anus land vagina and by subsequent retraction of the most mesial portion of the muscle to its present position. A considerable mass of cicatrical tissue 'iws present between the torn ends of this portion and the vaginal wall a n d in the interval between tlie torn edges of the group between anus a n d vagina. The ilio-coccygeus appears to be normal in its attachments, but is very thin and seems somewhat more degenerated than is usually found. The eoccggeus is the most dorsal muscle in the space. It is considerahly atrophied a n d most of its fibers terminate by a n apoiieurosis vlhicli extends backward t o tlie COCCyY. 190 200 WILBUR C . SNITH I n about 30 per cent of tlie bodies, inale and female, personally examined, a p a r t of the levator ani lies superficially to the posterior margin of the urogenital diaphragm. This part of the muscle is described when present as tlie superficial transverse peroneal. Almost every conceivable function has been attributetl to the levator ani muscle. I cannot agree with all the functions advanced. I do not think that this muscle has any perceptible function upon the coccyx, even though the opinion that it does is almost unanimous. While a considerable number of its fibers a r e inserted to tlie coccyx, it must be kept in mind that the coccyx has but very little movement in the joint between itself and the sacrum. Normally this is an ossified joint. It is, however, the principal, or the true spliiricter of the vagina. It acts also as a partial sphincter to tlie rectum in forcing out the contents of its lower end. It is the most essential single structure of the pelvic diaphragm ; its most important function being, as pointed out by Paramore, to resist intra-ab(1ominal pressure. SUMMARY I t is advanced that the pubo-rectalis muscle, a division of the levator ani, forms the real sphincter of the vagina; that the lumen of tlie anus is directed backward at an angle of about 80" with the long axis of the body instead of parallel with this axis, as many have pictured it; that the superficial transverse perinei muscles, when present, are fasciculi of tlie levator ani, and that iiiuch of the confusion concerning the levator ani is due to descriptions of it in inultiparous subjects claimed to have been nulliparous. THE LEVATOR AN1 MUSCLE "01 IiITERATURE CITED ALLEN, IIARRISON 1876 Xote on the anatomy of the perineuni. Trails. Colt. Physickiis, Phila., pp. 113-114. BRIGGS,€1. 1920-1921 The female floor. Proc. Roy. Soe. Med., Loncl., Sect. Obst. Gynec., vol. 14, pp. 197-206. BROWKING, W. W. 1897 A eontribution to the knowledge of the nnntomy of the levator aiii muscle. %fed.News, N. Y., vol. 70, pp. 789-791. BIAISDELL, F. E. 1917 The anatomy of the sacro-uterine ligament. Anat. Ree., v01. 12, pp- 1-42. c.4MEROX, J O H N 1908 The f:mm of the perineum :md tltc pelvis of the feni:ile. . Jour. Anat. and Physlol., vol. 42, ~ p 438-4.53. C. 1888-9 Edin. Med. Journ., rol. 34, p. 788. COE, HENRY 1901 Jour. Anat. and Physiol., vol. 35, p. 127. 1914 Jour. Obst. and Gyner., Brit. Emp., rol. 27, pi). 177-189. CLARK,11. It. 1911 Oiigin of musculature. Journ. Obstet. and Ggnec., Sept., p. 83. CLOQUET 1882 TiaitB d 'anat. descrip. Paris. CRUVEILHIER1874 Trait6 d 'xnatomie descriptive, 5th ed., Paris. DERRY,DOUGLASS 1907 Pelvic muscle and fascia. Jour. Anat. :1nd Physiol., vol. 42, pp. 107-111. DICKINSON,R. L. 1889 Studies of the levator a n i muscle. Amer. Jour. Obstet., hT.Y., V O ~ . 22, pp. 897-917. D I E U F A L ~I,., 1901 Origine e t coustitution dn muscle relereur de l'anus. J. de l'anat. et physiol., Paris, T. 37, pp. 385408. DORAN,A. 1886 A dissection of tlie muscles of the female pelvis and perineum. Obstet. Trans., vol. 28. ECKLEY, W. T. 1900 Anatomical refleetioils on tlie pelvic outlet. Chicago Clinic, vol. 13, pp. 20-22. 1900 Study and dissection of the pelvic outlet. Chicago Clinic, TO]. 13, pp. 168-217-288. FOSTER, F. P. 1880 Projection of the pelbic floor. American Jour. Obstet., J a n . FOTHERGILL, W. E. 1908 The support of the pelvic viscera: n review of some recent contributions of the pelvie anatomy with a clinical introduction. Jour. Obstet. a n d Gynec. of Brlt. Emp., Jan. FREDET, P. Peritoine morphogenese et morphologie. Poirier et A. Charpys, T. 4, fase. 3, ed. 2. FRANK, R. T. 1923 The treatment of cystoeoele, rectocoele and uterine prolapse. The Amer. Jour. Obstet. and Gyiiee., J a n . GEGENBAUER 1892 Anatomie des Mensehen, 5 A b s e h i t t : Muskelsystem, Allgemeines. Auflage, Leipzig. GOFFE, J. R. 1898 The anatomy a n d functions of the pelvic floor in women, a n d t h e operations f o r its repair. Med. News, N. Y. GOLDSPHON,A. 1887 Intrapelvic, intravaginal perinorrhaphy without loss Of tissue. Medicine, Geo. S . Davis, publishers, July. GRAFENBERG, E. 1904 Die Entwicklung der menschlichen Beckenmuskulatur. Anat. Hefte, Bd. 23, 8. 429-493. ~ 1 0 ~ d WILBUR C. SMITH GUBARELL, A . B. 1898 0 lazlloni dnie i promeghnosti (On the pelvic floor and perineum). J. Akush, i jensk, boliez. se Pelus. vol. 12, pp. 442-452. HARRIS,M. L. 1899 The repair of old lacerations of the pelvic floor. Jour. A. M. A., vol. 30, p. 1450. HART,D. B. 1880 The structural anatomy of tlie female pelvic floor. Eclinburg. Malaehlan & Stewart. Atlases of pelvic anatomy. HASSE 1886 Arch. f . Anat. HENLE Aiiatomie. HERMAN,C. E. 1889 Contrihutioli to the anatomy of the pelvic floor. Trans. Obst. Soe. Lond., published 1890, 1701. 31, pp. 263-275. HILL, HOWARD 1908 Restoration of tlie pelvic floor. Jour. A. &I. A., April 4, V O ~ . 1, pp. 1101-1108. HIS, W~LIIELM1878 Arch. f . Anat. HOGGE, A. 1904 Recherclies sur les muscles du pcrinei et du diapliragnia pelriii s u r les Ann. d. Rlal. d. Org. genitonrin. Paris, T. 22, pp. 1041-11‘21. HOLL, M. 1897 Die hluskelii urid Fascieii des Beckeiinusgxnges. Bardelcl~ens I-Iandbuch der Aiiatomie des Ifensclieiis, Bd. 7, J e x i . HOLSIES, E. W. 1900-1901 The levator a n i muscle. Proc. Am. Anat., rol. 1-1. KEITH, ARTHUR 1913 IIuman embryology aiid morpliology. 3d ed., London. KOIILMAX,J. 1894 Der coccygeus uiid der L e w t o r aiii bei den gescliwniiztcn A d e n und den Antliropoicleii. Aii:it. Aiiz., Ed. 60. KOULRAUSCH 1854 Zur Aiiatomie und Physiologie des Beckenorgaiie. S. 47-51. LAKTSCHNEIDER, J. 1805 Die Stcissbcinniuskelii cles Mensclieii u n d ilir Rezieliuiigen zuin I f . lerator a n i uiid zur Beckenfascie. Wicn. LESSITAFT1865 About the insertioii of the Iongit~ndinalmuscle fibres of the rectum. 1)iss. Spb. 1873 Ueber einige die Urethra. umge1)endeii Nusklcn und Fascieii. Arch. f. Aiiat. ron Rcicliert, S. 18. 1884 Ueber die Muskehi und F;iscieii iler 1)nrmgegend lieim JlTeibe. Morpli. Jahrbucli, Bd. 9, S. 480-490. L~JSCYIKA 18G1 Die Muskuhtiir am Boden des weiblichen Beckeiis. IVien. 1864. Die Aiiatomie des Menschen. Bd. 11, Alit. 2. D:rs Bcvkeii, S. 219-243. Tiibiiigen. hfailcu, €1. 0. 1888 The perineum, its :iuatoniy, plipiology :uid metliods of restoration a f t e r injury. Trans. Am. Assii. OlJstet. and Gynec., Phila., pp. 69-93. &fAeTIN, EDOUARD 1011 Uer Heftapparat der wt?ibIiclien Genitalien. Berlin, rerlag von S. K:irger, Karlstrasse 13. MECKEL’SAnatomy, vol. 3, ed. 1832. MERIEL 1900 Le releveur de l’anus et le relapsus pclrieus. Gaz. Iiebt. de ined., Paris, n. s., T. 5, pp. 1117-1123. NOBLE,G. €1. 1903 A new method of suturing the fascia aiid lerator aiii muscle in perineorrlinpliy ; :ilso, a n operation for complete laceration of the perineum, designed f o r the purpose of eliminating daiiger of iufection from the revtuni. Am. Gynec., 3f:tr. OWEN Anatomy of vertebrates, rol. 3, Mamin:rli:i. THE LEVATOR AN1 MUSCLE 203 PARAMORE, R. H. 1910 The evolution of the pelvic floor in the non-mammalian vertebrates a n d pronograde mammals. London Lancet. 1908 The supports in chief of the female pelvic viscera. London Lancet. PATTERSON, A. M. 1907 The nieclianical supports of the pelvic viscera. Jour. Anat. a n d Physiol., vol. 41, pp. 300-311, July. PICHETIN, R. 1900 Statique pelvienne et planeher pelvian. Semaine Gynec., Par. RAXEY 1882 Topogra1iic;tl relatioils of pelvic organs and female perineum. N. Y . Med. Jour., July. RETTERER, E. 1890 Sur l’origine et l’evolution cle la region anogeiiitale cles mammiferes. Jo u r n . de l’anat. et de la Phys., T. 26, pp. 126-153. ROBINSOX,R. B. 1898 Jour. A . M. A., vol. 31, pp. 389, 646, 716, 782, 8.56, 921, 972. SAPPEY1895 Trait6 d ’nnatomie descriptive, 4 ed. Paris. SAVAGE, €1. 1880 Female pelvic organs. Wm. Wood & Co. SMITH,ELLIOTT1907-8 Studics in the anatomy of the pelvis with especial reference t o the fascia1 and visceral supports. Jour. Anat. and Physiol., vol. 42, part 1, pp. 198-218; p a r t 2, pp. 250-270. SPALTEIIOLTZ, WERNER 1903 Handatlas drr Anatomie des 15enschcn. Bd. 3. Leipsig. STARKOFF, A. V. 1904 General anatomy of the male pelvis. Khirurgin Jloask., vol. 15, pp. 3-10. STUDDIFORD, W. E. 1902 Anatomy of the levator ani. Am. GSiiec. and Pediat., Boston, vol. 13, pp. 260-263. S u w o x , BLAND 1902 Ligaments ; their nature and morphology. 3rd ed. London. SYIIIXGTON, J. 1885 A contiibution t o the normal anatomy of the female pelvic floor. Edin. &led. Journ., vol. 24. TANDLER A N D HALBENAnatomie uncl Etiologie des genital Prolapse beim Weibe. Vienna and Leipsig. TESTUT,L. Trait6 d’anatomie humaine. T. 33. THOXPSON,PETER1901 On the arrangement of the fascia of the pelvis and their relationships to the levator ani. Jour. Anat. and Physiol , vol. 33. 1906 Studies from the anatomical department of the University of Manchester, rol. 3. 1889 The myology of the pelvic floor. Manellester. 1900 The pelvic diapliragm. Studies from the anatomy department of Owens College, vol. 2. S-EvhDEssIm, A. A. 1893 The diaphragm of the pelvis and its import:rnce. N e d . Obozr. Xosk., vol. 40, pp. 337-349.