The effect of fat in simplified diets on the reproductive organs of the female albino rat during gestation.код для вставкиСкачать
THE EFFECT O F FAT I N STAIPTATFIEDD l E T S ON THE REPRODUCTIVE ORGAN3 O F THE PEhIRLE ALBIKO R’AT DTJRIXG GESTATION OKE FIaI‘RE INTRODECTION Interest has recently been stimulated by the low-fat studies of Burr and Burr, and Evans and Lepkovsky, on the relationship betweeii f a t cleficienc-y and disturbances in reproduction. The present investigation was undertalien to study in ctctail the effect of fat-poor diets upon the reproductive organs of the femdc alhino rut during gestation. T wish to tlianlr Dr. Jenniiigs C. Litzenberg, Dr. c‘. 31. Jackson, Die. Georgc 0. Burr and Dr. W. R. Bi-owii for their invaluable advice and criticism during the course of this investigation. MATERIlL AND BIETI-IODS Eighty-seven female albino rats (Mus norvegicus albinus) of the ~ ~ i n n e s o t a - T ~ ~strain i s t a r were used in the experiments. The females m e ~ ebred from stock animals reared on McCollnm’s diet no. 1, and were placed o n diet 551-B (Brown and Burr. ’36) at tvenning. The weaning weight averaged 44 gm. Diet 551-I5 consists of : 84.1% siicrose (eommercinl) 12.n<& crude casein 3.9% salt mixture (McCollum’s no. 185). Accepted in partial fulfillment of the requirements f o r the degree of doctor of philosophy at TJniversity of Minnesota. 73 TRB A N . ~ T O ~ I I C % mLr n m , T - m . 7 0 , NO. 1 A N D s r m r , m r x N i ’ NO. 1 74 EDWARD C. MAEDEII I n addition, each animal was individually fed 0.65 gm. of ether extracted d r y yeast, 14 y of British Drng House ‘A,’ riosterol equal to 2 drops of high grade cod live^* oil, and the nonsaponifiable matter from 36 mp. of wheat germ oil. The rats were weighed ~~-eelcly undcr carefully standardized conditions. A t regular inter\-& following maturity, orulation cycles were determined in order to rlassify the oestrous beliavior of each animal. TVhe~ibrcediiig was desired, the females at the pro-oesttrons stage Twre placed in the cage o i a tested male and allowcd to remain over night. Tlie first day of pregnancy was coiisiderecl as tlie clay following that on mhich the vaginal plug o r sprrmatozoa were observed. l’ositiw pregnancy was diagnosed by the appearance of ‘red blood-cell sign’ from the tliirteenth to fifteenth day following insemination. Daily weights were recorded during gestation in order to detect resorbing pregnancies. After R definite plateau in weight liacl been rcaclied the animals were clirided into two groups. The first group of forty-one animals was Bcpt on a low-fat diet ; the second g r o ~ i p of sixteen animals ~ v a sfed a supplement of fresh lard daily. These were then used laicr as the ‘cared’ controls. A third group of stock control aiiimwls (Minnesota-T;C’istar strain) wits used a s a comparative staiiclavd for the ‘cured’ control animals. ,4 f o u r t h small group of ‘ciired’ control animals was later furnished from the l o w f a t experiments of Brown and Burr. These aniinals diffcrccl from tlie second group in that the protein lcrel was 24%) crude casein and the lard dose 10 instead of 20 drops. Animals from these groups were Idled on successive days of pregiiancy from the seventh to the twenty-second day. In tlic Iosvfat group, d i e r e prolonyed gestation was observed, aiiiitials were sacrificed daily, up to and including the twentpsixth day. The preparation o i material f o r microscopic cxarnina1’1011 consisted in the removal of tlie ovaries and the embryos o r resoi*ption I)odies with a corresponding segment of tlw uterus. These were fixed in Bouin ’ s solution, cleared aiid dehydrated in diosan solution and embcddcd in paraffin by the usual methods. The early specimens were sectioned and mounted seriaIlJ-; in the larger. ones, every tenth section was mounted. Hcmatosyliii and eosin were used to stain all sections. THE CIIARACTERIHTIC8 O F H A T 8 1iEARHI) ON LOW F A T DIETS T’lie cliiiical appearances a d characteristics of such fatpoor aiiimals conformed closely willi thosc of Burr and Brown, whose animals were reared on the same diet in an adjacent coloiiy room, The rats used in this investigation sho-\wclfat deficiency symptoms o n l y t o a moderate degree. Tlie scaliness of tlie feet was not serere and the tail lesions were not the most marked. A t autopsy marked renal lesions were not routinely found, and although the mesenteric fat v a s absent o r very scant, the omcntal fat, as a rule, was abundant. No indication of xerophthalmia occiirred. The animals on tlie low-fat diet were not hyperactive and, although weighing only $OFl as much as their controls, consumed about. the same amount of food. It was found that the fat-poor animals consumed daily over two times tlie amount of water averaged by the controls. According t o Burr and Burr (’30) thc excess water consumption is cvaporalcd from the lungs and skin. The animals placed on a low-fat diet at weaning did not show any great retardation of growth during the first 60 days. As was previously reported by Burr aiid Burr ( and ’30), the animals were always somewhat subnormal in size and readied a growth plateau earlier than normal. They started t o plateau a t about 4 months of age at a weight of approximately 156 to 158 gm. (fig. 1). After being placed on a cure of 20 drops daily, o r approximately 4% of fresh lard, which contains about 7% of the essential liiiolic acid, the deficiency s:-mptoms started t o disappear. I n 3 or 4 weeks the scaly condition of the feet cleared up. Tlie tail lesions disappeared, and there was a marked clearing of tlie skin. Dandruff disappeared a n d the hair coat became improved. Renewed growth both in length and weight (fig. 1) occurred almost immediately. B u r r and B u r r (’30) observed that orulatiori is often irregular or ceased entirely in fat-free animals (diet 550-B). When a curative oil is fed, ovulation is resumed. Female rats on the fat-free diet will mate whcn ovulation occurs. The added oils so improve the animals as a whole that ovulation is resumed. From the observation of 402 cycles of fifty-seven fat deficient animals, 80.35c/, were found t o be of 3, 4 and 5 clays duration. After sixteen animals from the above group had been on a cure for several weeks, 115 cycles were further studied, of which 96.53% were of the same duration. Only three of the ‘cured’ control animals were allowed to litter. Parturition was normal ; two of the litters were allowed to lactate and were subsequently successfully weaned. GRCSS CHANCE8 I N T H E REPRODCCTIVE ORGAn’S O F P A T D E F I C I E S T RATS The control ‘c11red’ and normal stock animals revealed 110 essential difference in the gross nature of the reproductive organs and their contents. In the pregnancies that failed to reach term, the abnormal enlargements were of’ a softer consistency and of a blue color, in marked contrast to the purple color of normal pregnancy. The blue discoloration was due to blood in the amniotic cavity. In the older resorptions the enlargements became more fusiform in shape and assumed a bluish-black color. When opened, they revealed only dark blood stained debris. Frequently copious hemorrhage into the lumen of the uterine horns was observed. The decidual bodies (Dnval, 1891) at the inesometrial border were relatively prominent. The great variation in the size of‘ the uterine pregnancy sites indicated that the beginning or rate of resorption was by no nieans uniform. The conditions encountered were wholly iinpredictahle. Frequeiitly dead and resorbing fetuses were intei*mingleed with others whose gross appearance was normal. When all, or a portion of the fetal sites failed to undergo early resorption, growth of the fetus mas often retarded and fetal death occurred at different periods during late pregnancy. ISecause in the fat deficient group of animals no incidence of successful parturition was encountered, it is believed that the normal sites observed at the different stages of pregnancy would have eventually succumbed either to resorption in utero or t o late fetal death with or without delivery. TT’hen resorption did not occur the pregiiancies were frequently prolonged to the twenty-fourth, twenty-fifth and twenty-sixth days. If the resorption occurred late in pregnancy, or if there was prolongation of gestation, excessive ainounts of dark brown, tarry-colored exudate with some necrotic cellular debris was u s u a l l ~observcd in tlie vaginal smears, resulting in a delay in the reappearance of oestrus indicating some pathology of placentation. I n a few cases of 78 EDWARD C. MAEDER early resorption blood was noted prematurely in the vaginal smears several days prior to the appearance of the red blood sign. I n the few animals that were delivered after prolonged gestation some difficulty in parturition with increased bleeding was noted but none of the animals died. I3owever, during the period of prolong~dgestation, the animals appeared weals, inactive and listless. Periods of prolonged gestation usually terminated in the dclivcry of a variable number of dead and living fetuses. The litters were usually small and under-sized. The decrease in the average number of young per litter was due t o a sporadic resorption of fetal sites during the early stages of pregnancy and also to an apparent relative failure of implantation. Growth of the fetuses in utero was quite rarinble. The live fetuses appeared weak and anemic, usually succurnbiiig a few hours after delivery. In the prolongation of' gestation the placentas appearcd dark and hemorrliagic. They were of soft consistency and varied in size. The amniotic fluid disappeared, in some instances, being represented only by a fern strands of a stringy, tarry-colored material. I n some cascs the fetuses were cast inside with the membrane intact and mitli the degenerating placenta adherent outside. The fetuses in these cases were removed with difficulty from the dry amniotic sacs. S o gross evidence of pus was noted. Hemorrhage and edema, of the uterine wall were i'reyuentlp observed suggestive of the ' Couvelaire uterus ' seen in human cases of prematnre separation of the placenta. The ovaries of the lotv-fat animals where resorption and prolonged gestation occurred showed cliaracteristic gross clianges. The corpora lutea of pregnancy appeared larger, paler and became chalky white in color. The ovaries showing these signs of degeneration weighed relatively more than those of the controls. No iicw o r extra corpora lutea were observed in prolonged gestation. REPRODUCTION IK FAT D E F I C I E S T RATS 79 NICROSCOPIC CIIRXGES I n some of the fat deficient animals, blood mas observed early in the uterine lumen, soon aiter implantation had occurred. Free blood in the uterine lumen dnring early stages of pregnancy has been found by Huber ('15) in uteri possessing- an abnormal endometrium. Evans, Burr and Althausen ('27) noted in pregnant E-free mothers on the eighth day of pregiancy extravasated blood in and about the free lumen of the uterus which lies mesometrial to the dccidual cavity in which the egg is found. The placenta gave a varied histological picture. Areas of localized hemorrhage from rupture of the maternal blood sinuses were commonly observed near the periphery of the placenta with exudation into the uterine cavity. Distension and rupture of the vascular sinuses of both the maternal deciclua and fetal tropholnlast were frequently seen, possibly due to an increased permeability of the vascixlar endothelium. Edema was often rioted associated with the vascalar congestion arid hemorrhage in both the uterine wall and placenta. Following this severe hemorrhage and decidual in jury, areas of necrosis of varying iiitensity were observed, starting usually at the maternal side of ilie placenta and progressing toward the fetal surface. The maternal tissues were prim a d ) - in\dved more than the fetal structures. Areas of focal necrosis were occasionally observed in the decidua near the region of the trophoblast. In cases of early resorption no definite evidence of infection mas encountered. However, in the late resorptions and cases of prolonged. gestation considerable evidence of inflammation, most likely secondary in nature, was observed. These areas of focal and diffuse exudation were associated with the process of necrosis. Both of these processes seemed to occur secondary t o the hemorrhagic lesions. The histological picture \$-as both that of ail acute polymorphonuclear and polyblastic type of inflammation. I n some sections only granulocytes and macropliages in varying proportions were observed, while in other sections a more low grade type of inflammat'ion 80 EDWA1:D <:.MAEDEIZ with a predominance of lymphocytes and plasma cells w7as observed. The leukocytic infiltration mas most common and intense usually at the junction of the placenta and chorion forming along with the associated necrosis, a ring around the periphery of the placenta. I n many instances tlie leukocytic infiltration extended into tlie uterine wall. I n animals autopsied hefore the process of resorption had been initiated, normal anatomical development of both the placentas and fetuses was obsprved. Except in cases of early resoi*ption, the yolk sac with its entodermal villi, allantois, and other fetal structures showed normal development. I n cases of prolonged gestation, tlic yolk sac structure could still be readily identified. Hematopoiesis and differentiation of fetal tissues revealed a normal histological picture. No failure of mesodermal elements was observed. I n spite of severe placental injury, very little retardation of fetal development was observed. Marked decidnal and placental injury in\-ariahly preceded the alteration in the fetal tissues. The fetal injury consisted of general disintegration of the tissues due to lack of nutrition subsequent to placental injury. I n late resorptioris and prolonged gestation, where the disease was leas acute, late fetal death and general retardation of fetal development was observed. The intermuscular and mesometrial deciclual reaction of the decidual body was delayed in the process of resorption, as compared with the control sections, still being visible a t the end of pregnancy and in prolonged gestation. It regr by lympliocytic aiid leukocytic invasion aiid often extrarasation of blood was noted. a b o u t the same time that abnormal histological finclings were noted in the placenta and uterus, microscopic changes in the ovary were first observed. The lnteal cells becanir coarsely granulatd, clear and vacuolated ; they swmed to lose their affinity f o r the eosin stain, and developed a foamy appearance. Vacuolization arid coarse granulation of the luteal cell do not normally occur until about tlie seventeenth REPRODI’CTION IX F A T D E F I C I E S T RATS 81 day of pregnancy. By the end of pregnancy degeneration is moderately advanced, but many luteal cells retain their normal structure. No new corpora lutea or maturation of the graafian follicles were noted in the cases of prolonged gestation and late resorptions. Oestrus was considerably delayed in cases of prolonged gestation and late resorptions. Only in some instances of early resorptions did ovulation reappear before the end of the usual gestation period. DISCT~SHIOK Rats used in this investigation and reared 011 diet 551-B developed typical fat deficiency symptoms. Brown and Burr (’36) stated that relatively impure diets may be used for the production of typical fat deficiency symptoms. When crude casein is substituted €or purified casein, the weight at the time of plateau is slightly higher and decline and death are postponed. However, hematuria, scaly feet, and scaly and necrotic, tails still occur i o almost the same extent. The process of reproduction was early impaired and was more resistant to treatment with curative doses of lard, u~hile ovulation was affected late and returiiecl t o normal a €ew weeks after the animal received the lacking dietary unsaturated fatty acids. The dosage of the oil fed seemed to affect also the rate of cure. Two 01 the ‘cured’ animals (Alaeder) after receiving 20 drops of lard f o r 95 days, had successful litters, while some of the Brown and Burr ‘cnred’ rats, after receiving 10 drops of lard daily for over a year, failed t o reproduce although manifesting external clinical cures. This plienomena is probably rxplainecl on the basis that pliysiological cures are not as rapid as external o r clinical cures. Hansen and 131-own (’37) have shown illat animals given small quantities 01the methyl estcrs of liiiolic acid suficient to affect clinical cixres were found to have a vcry little change in the iodine number of the total blood lipids. I n general, once the physiology of reproduction was definitely iiitcrfered with, considerable difficulty was encountered in aEecting an internal cure. In some cases the contlition secmcd irrc~parablc. 82 EDWARD C . MAEDER Lowfat diets resulted in atrophic clianges in the uterine mucosa and maternal deciclua, interfering with the nutrition necessary f o r the satisfactory nidation of the fertilized ovum, and f o r the successful continuation arid termination of gestation. A definite relative decrease in the number of implantation sites was apparent. These observations suggested some disorder of implantation, due most likely to a lack of hormonal stimuli, which interfered with uterine nutrition. If the fatty acids are associated with the ovarian hormones, it is possible that on a fat deficient diet the syuthesis of ovarian hormone may be impaired. When the fetal sites failed t o undergo early resorption, fetal death occurred a t different times during late pregnancy often resulting in prolonged gestation due to abnormalities of placentation wliich were frequently associated with copious hemorrhage. Variation in the size of tlie placeiita with hemorrhage, tissue necrosis and infection in tlie placenta and iaterine wall WXR often noted. These atero-placental changes are similar to these noted by Mason ('35) in ritamiii 'A' deficiency and by Ueno ('34) where there was a lack of vitamin B. In prolonged gestations there was a significant decrease in the average number of young per litter and a marked variation in the size of the dead and living fetuses delivered o r observed at autopsy. Death of the fetus during the latcr stages of pregnancy mas attributed t o a less acute manifestation of the same factors responsible f o r earlier resorption. However, the small litters were usually uiidersized and the living young anemic, weak and of impaired vitality. According t o King ('15) it is possible that prolongation of the gestation period for even 1day materially increases the weight of the young at birth and further adds that individiials in small litters weigh more at birth than do individuals in large litters. Prolonged gestation up t o 26 days and difficult parturition was frequently associated with copious hemorrhage and great weakness of the mother. These findings agree with those of Evans and Lepkovsky ('34) and are similar to the observations of Mason ('35) on the prolongation of pregnancy and REPRODUCTION IN EAT D E F I C I E N T RATS 83 the associated phenomena in vitamin A deficiency. KO signs of xerophthalmia, abnormal vaginal cornification, o r any other indication of vitamin A deficiency were observed. Similar prolongation of gestation was also rioted by Barry ( '20) in rats coming to term after underfeeding from the eleventh day of gestation. However, in view of the large proportion of deliveries observed by Barry ('20) in rats in wliicli inanition was much more severe than in our fat deficient rats, there is no reason to believe tliat growth retardation played a significant role in tho reproductive disturbances. On tlie other hand, Burr and Browii ( ' 3 6 ) report that when fats high in unsaturated fatty acids are fed, the gestation period tends to be less than that found f o r normal stock animals. The prolongation of gestation and difficult parturition is apparently due in part to deereased vitality and death of fetuses during the late stages of pregiizancy. Another contributing factor is the general weakness of the mother, associated with decreased tone of the abdominal musculature. Decreased responsiveness of the uterine musculature due to lack of necessary liormonal aiid mechanical stimulation is ailother important consideration. Furtliermore, toxicity arising from tlie aiitolysis of the placental aiid fetal tissues must be recognized. I n the fat-deficient animals, secondary fetal death is best cxplained on the basis of decreased nutritive supply as a result of hemorrhage aiid tissue injury in the placenta and uterine wall. In vitamin A deficiency blason ( ' 3 5 ) wriles that fetal death is also secondary to marked placental injury. There is no interfercnee primarily with tlie development of the fetal structures a i d hematopoiesis as in vitamin E deficiency. According t o Eraiis and Burr ( '27) aiid Uriier. ( T l ) , lack of vitamin E produces a retardation of clevelopment and differentiation of the fetal tissue, with no direct involvement of the maternal tissues. It was particularly rioted that in some of tlie partially 'cured' control group, which had first been bred before a physiological cure had becii affected, that ovulation was considerably dclaycd follomiiig the process of late resorption. It 84 EDWARD C. MAEDEIL seems that postpartum oestrus is considerably clelaped by tlie preseiicc o i retained intra-uterine gestational products. Tlicse same aniinals often showed bloody vagiiial smears due to excessive uterine bleeding for many days following the expected date of delivery. Newton ( ' 3 5 ) states that the placeuta plays an essential part in the inhibition oP oestrus during the latter half of pregnancy and probably also determines the date of parturition. After delivery of t h e placenta (pseudoparturition) oestrus occurs in 1to 2 days. Coincidentally with I h e placental change, alterations both grossly and microscopically were observed in the ovaries. In the fat deficient rat (luring prcgiiaiiq- the degenerating ovaries became relatively larger and heavier than those found under normal pregnancy conditions. In cases of late pregnancy resorptions and prolonged gestation, the ovaries appeared pale, prominent and chalky. Evans and J q k o v s k y ('34) noted that the ovaries of fat deficient rats in cases of prolonged gestation very frequently had an unnatural white, chalky appearance. lllasoii ( ' 3 5 ) found in rats autopsied after prolonged gestations that the ovaries usually contained very pale and prominent corpora lutea. Microscopically, these large chalky corpora lutea rerealed degenerative changes in the luted cells which hecome clear and vacnoliaed, presenting a foamy appearance. Some of the cells besides losing their affinity for the eosin stain, become coarsely granulated. This histo-pathological picture corrcsponds to that observed hy Kasper ('31) in vitamin F: deficient rats. Mason ('35) removed the oraries of vitamin A deficient rats between the eighteenth and twenty-first clays of pregnancJaiid failed to demonstrate any lessening of the abnormalities of late gestation in tlie olwratecl rats, thus ruling out hyperfunction of the corpora lutea as the cause of prolonged gestation. Prolongation of gestation and abnormalities of parturition have been observed by Snyder ( '34) in rabbits in which an adclitional set of corpora liitea was induced by iiijcction of extracts of pregnancy urine (Aiituitrin S) near term. A normal number of corpora lutca was oljserved in the low-fat REPBODLTCTION IN FAT D E F I C I E N T BATS 85 animals hotli grossly and microscopically. The ova and developing graafian follicles revealed no histo-patholog?. Thew degenerative changes both in the ovaries and placenta appear to occur concomitantly, apparently resulting from the same etiologic basis, probahly due to a lack of proper ovarian hormone synthesis and improper endocrine balance. From extensive experimentation with rats, Selye, Collip and Thomson ( '35) conclude that the placenta furnishes the necessary stimuliis f o r the maintenance of the corpus luteurn of pregnancy and determines the length of prcgiiancy either by its effect on the corpus lutenrn or by its own progestin production, or which is more likely, by both of these means. They further found that in the rat ovariectomy during pregnancy does not interfere with the life of the placenta. It terminates pregnancy only because it causes the death of the fetus probably due t o partial involution of the uterus which considerably increases the pressure in the gestation sac. The life span of the placenta was not markedly influenced by the removal of the embryo. The length of the gestation period must be determined hy factors inherent in the placenta. The decidual body appeared more prominent both grossly and microscopically in the pregnant fat deficient animals. TJrner ( '29) noted the same findings in the failed pregnancies of vitamin F: deficient animals. As a practical aspect of the study it might be well to point out at iliis time that as Burr arid Burr ('30) suggest, the human diet is often exceedingly low in fats of any kind and that when fats are added they usually contain little of the acids more unsaturated than oleic. It is possible that our high carbohydrate and protein diets, carrying very little of the unsaturated oils, a r e contributory factors to poor health and sterility. The addition of egg yolk and cod liver oil to diets may often improve the patient because of the fatty acid rather than the vitamin content. F o r example, cures of anemia with cod liver oil have been reported and it has been sliotvn that there is a relation between experimented anemia aiid uiisaturated fatty acids of the blood plasma. The preralence of dry skin and abiiormal kidneys may be directly attributed t o improper fat intake. As the liver is apparently limited in its ability to produce these acids, they should be plentifully supplied through the diets. XUMhl AK Y 1. Animals reared on diet no. 551-B sliowed the typical characteristics of tlie f a t deficiency syndrome. 2. Reproductive function is early impaired on a f a t clcficient diet. The findings substantiated tlie observations of Burr and Brown, that reproduction was n o t normal until some time after a clinical cure had been obtained. 3. Ovulation is impaired late on a fat-poor regimen, but responds early t o curative doses of uiisaturated fatty acids. 4. A definite relative failure of implantation was observed, due t o atrophic changes and undevelopment of thc uterine miieosa and maternal decidua. 5. Resorptions o r prolonged gestation resulted from fat deficient diets. No successfiil gestations were obtained with fat deficient animals. 6. His tologically, rariable degrees of hemorrhage, necrosis and secondary inflammatory csuclate were observed in the placenta and uterine wall. '7. In fat deficiency, fetal death was secondary to marlred placental injury. 8. Early interruption of gestation frecjuentlp occurred if the fat dcficiency symptoms TIYW very acute. 9. I n less acute fat cleficimcy, prolonqed qcstation occurred. 10. Prolonged gestations n'ere frequently associated with excessive uterine bleeding, difficult partnritioii and great weakness of the mother. 11. T,essenecl vitality or death of fetuses, decreased tone of tlie abdoniinal and uterine musculature, and possihle lack of the necessary hormonal stimulation, were reo.ardecl as the h important etiologic faetors of p r o l o n g d gestation. REPRODTJCTION I S FAT DEFICIENT RATS 87 12. Degenerative changes in the ovaries of fat deficient animals occnrred conconiitaritly with the ntero-placental pathology, The large chalky ovaries, commonly observed, microscopically showed vacnolization and coarse granulation. 13. The decidual bodies arc prominent i n prolonged gestation and late resorption. 14. The failure of reproduction in linmaiis due to lack of adequate fat in the diet is considered possible. LITERATURE CITED BARR\, Td. W. 1920 The effect of inanition in the albino rat with special refcr ence t o the changes in the relative weights of the various parts, systems and organs of the offspring. Contrih. to Embryol., vol. 13,pp. 91-136. BROTTP;, W.R., AND G. 0. BURR 1936a Some reeeiit studies in f a t deficiency. J. Biol. Cliern., Proc. d n i . Soc. Biol. Clieni., vol. 114, p. 16. 1 9 3 6 b Some effects of quality of f a t s on their nutritional value. Papcr read at Kansas City hrfore the Biological Section of the Anieri can Chemical Society. BURR,c. O., AND &I. &I. BURR 1929 il new deficiriicy disease produced by rigid exclusion of f a t from diet. J. Biol. C'hnn., 1701. 62, pp. 345-367. 1930 On the nature and role o f f a t t y acids essential in nutrition. J. Biol. Cheni., vol. 861, pp. 587-621. BURR,G. O., AND W. K. BKCJ!%X 1933 On f a t t y acids cssential i n nutrition. Proc. Soc. Exp. Biol. xiid Rled., vol. 30, pp. 1349-1352. UTWAL, Al. 1889-1892 Le Placenta dcs Rongeum. J . de l'anat. et d~ la Physiol., T. 29-30. Ev-~xs,H. M., (4. 0. Bus& I N D T. ALTWAIJSEN1937 The antisterility vitamin f a t soluble E. hlemoirs of thc University of Calif., 7701. Y. 1927 New dietary deficiency n i t h highly pu'ifird diet?. 11. Supplementary requirements of diet of pure easoin, sncrose and salt. Proc. Soe. Exp. Bid. and Med., col. 25, pp. 4 1 4 8 . 1928 A new dietary deficiency wit11 highly purified diet.;. 111. The beneficial effect of f a t i n diet. Proc. Soc. Exp. Biol. and RIed., vol. 23. pp. 390-397. F h A N S , 11. hI., A N b 8. T 2 ~ ~ ~ 1932 ~ ~ r T iqt e ~l nwd ~ 7 of the body f o r certain umaturated f a t t y acids. J. BioI. Chem., vol. 96, pp. 143-155. 15124 Vital need of the body f o r certain unsaturated f a t t y acids. I. lieproduction and laetation upon fat-free diets. J. Biol. Chem., vol. 10G, pp. 4 3 1 4 4 0 . H - ~ N s ~A. N , E., ABD W. R. BROWN1937 Effect of dietary f a t s npon ser111n lipids of rats. J. Sutrition, vol. 13, pp. 351-357. €€VDEI~,G. C . 1913 The developlent of the albino rat (Rlus noneegicns albinus). J. hlorph., vol. 25, pp. 24i-35P. I ~ A R PE. E R&I. , 1931 The gcnital tract of thc rat, with special rcferencc to changes i n prrgn:mcy and during vitainin E deficiency. Thesis, Gtaduate School of the Univ. of Mian. 88 EDWARD C. MAEDEB KING,H.D. 1915 On the weight of the albino rat a t birth and the factors that MASON, influence it. Anat. Bee., vol. 9, pp. 213-231. X. E. 193s Foetal death, prolonged gestation, and difficult parturition in the r a t a s a result of vitamin A deficiency. Am. J. Anat., vol. 57, PI).3 0 3 3 4 9 . NEWTON,1%’. 11. 1935 ‘Pseudo-p~rturition’i n the niouse, and the relation of the placenta to post-partuni orstius. a. Physiol., vol. 84, pp. 196-207. SELPE,H., J. B. COLLIP - 4 m U. L. THOUSON 1936 Endocrine interrelations during pregnancy. Endocrinology, vol. 19, pp. 151-159. SNYDEIL, F. F. 1934 The prolongation of pregnancy and complieatons of parturition in rabbit following induction of ovulation near term. Johns Hopkins Hosp. Bull., vol. 54, pp. 1-23. UENO, d. 1934 Exprrimental study of the effect of vitamin B i n the f c m d e genital organs. J a p . J. Ohstet. a n d Qyn., vol. 17, p. 388. UHNEE,J . A . 1931 l’hr iiitra-uterine changes in the pregnant albino rat (Mus norwgicus) deprived of vitamin E. Anat. Eee., vol. 50, pp. 175-187.