THE RELATIVE V~EIGHTOF THE TESTES I N PRIhIATES $DOLF’II 11. SCIIULTZ L a b o r a t o r y of Physical A n t h r o p o l o g y , Johns I I o p k i ~ i s Mrdicnl School, Baltimore, X u r y l a n d The relative size of the testes varies very strikingly among different primates. I n order to gain some accurate information on this subject the author had collected some relevant data at differelit occasioiis during the past few years. Last year it became possible to increase this series of data to an extent resulting in definite conclusioiis. Thj opportunity arose during the Asiatic Primate Expedition of 1937 of which the author was a member.l Fiftyfive of the adult male primates, recorded in thc accompanying table, were weighed and autopsied on this expedition. Observations on seventeen other monkeys and apes (mostly from the Hoplziiis comparative-anatomical collection) hare been added, as also data on three Negroes (unclaimed bodies of the anatomy department of the Johns IIopkiiis University). Corresponding data from the literature could be found only in a paper by Hrdli6ka ( ’as), who has listed the weights of the bodies and of the testes in seven adult howling monkeys from the field notes of the late Xr. J. L. Baer. The preseiit paper records the relative weight of the testes in a total of eighty-tvo simian primates. The testes alone, without the epididymides, are considered herc. The first twelve primates listed in the table are platyrrhines o r New World monlreys. All the others are catarrliines. This expedition was orgnihcrl by Mr. H. J. Coolidge, Jr. The (larnegie Tnstitutioii o f Washiiigton generously eoiitributed a grant toward the author’s expenses 011 this expedition. 387 Weights of body and of tca-tes n.ad percentage relatlon hetween. tlse t w o Wt?fghtS PIL crglitu adult and two juvenile pitinates smcim Ocdiponiidas geoffr0.i Aotus zonalis Alouatta palliata Alouatta palliata Alouatta palliata I Alouatta palliata Alouatta palliata Aloiiatta palliata * Alouatta palliata Alouatta palliata Average of 8 Alounttn Lagothrix lagothricha Ateles geoffropi Macaea irus Macaca irus Macaca irus Macaca h i s Macnca irus Macaca inis Macaca irus Macaca irus Macaca irus Macaca irus Macaca irus Macaca irus Average of 1 2 Macaca irus Macaca philippinensis Maeaca phiIippiiieiisis Macaca radiata Macaca nemestrinus Macaca mulatta Macaca mulatta Papio sphinx Pygathrix cristatus Pygathrix cristatus Pygathris cristatus Pygathris cristatus Pygathrix cristatus Qgathrix cristatus Pygatlirix cristatus Pygathrix cristatus Pygathrix cristatus Pygathrix cristatus Pygathrix cristatus Pyga thrix crista tus Pygathrix cristat us Ppgathrix crista tus Average of 14 Pygathrix cris. ;OXTDITIOI w. p. w. p. w. p. f. m. f IT. . w.f. f. w.f . 1'. f. w. f . M'. e. p. w.p. w.f . f. m. f . w. f . TV. f . R. w. f . w, f . w.f . w.f . w.f. w.f. p-.f . tv. p. w. p. c. f . m. f . c. f . e. f . c. p. c. p. nr. f. w.f . w. f. IT. f. w. f. TV. f. w.f . w.f . w. f . w. f. m. f. w.f. w. f . 388 BODY WEIGHT TESTES WhlCHT Izg. gin. 0.37 1.02 - c 1.12 6.92 7.03 7.03 7.26 7.26 7.48 7.82 7.SB 3.33 7.94 1.8 1.2 24.8 30.1 21.3 24.8 26.6 19.5 24.8 28.3 25.U 11.2 13.4 0.316 0.118 0.321 0.435 0.303 0.352 0.366 0.268 0.331 0.362 0.313 0.215 0.169 3.63 3.85 3.85 4.30 4.30 4.54 4.54 4.76 4.98 4.98 5.44 5.44 4.55 4.31 4.53 8.40 9.98 9.98 10.88 31.98 19.6 18.9 17.8 27.9 36.0 37.8 2 i.4 43.8 26.9 36.4 36.8 39.7 0.540 0.491 0.463 0.648 0.837 0.833 0.604 0.920 0.540 0.731 0.676 0.7.30 0.668 0.800 0.794 0.686 0.668 0.742 0.717 0.278 4.77 4.98 5.67 5.90 5.90 6.13 6.35 6.58 6.58 6.58 7.03 7.48 7.48 7.94 6.98 2.8 0.6 5.0 6.6 4.8 5.4 6.3 7.0 5.5 7.8 5.9 6.7 6.1 7.0 5.5 30.8 34.5 36.0 57.6 66.7 74.0 78.0 88.9 'ERCENTAGE 0.059 0.012 0.088 0.1 12 0.081 0.088 o.nw 0.106 0.084 0.118 0.084 0.089 0.081 0.088 0.085 SFRCIRS ONDITION BODY WEIGHT TESTES IVEIGIIT kg, ym. EZOENTAGE ~ Pygathrix rubicundus Pygatiirix rubicundu9 Pygathrix rubicundus Py g athrix r ubicundus Pj-gathrix rubicundus Pygathrix rubicundus Pygnthrix rubicundus P ? gathrix rubieuiidus Pygathrix rubicundus Pygatlririx rubicuiidus Pygatlirix rubieuiiclus Pygathrix rubicuiidus Average of 1 3 P:gatlirix rubie. Nasalis larvatus Nasalis l a n a t u s Nasalis larvatus Nasalis larvatus Nasalis larvatus Nasalis larvatus Nasalis larvatus Sasalis larvatus Average of 8 Nasalis lnrvat. HJ-loba tes Hylobates Hylohates Hylobates Hylobates cinereus cinereiis chereus cinereus cinereus Hylobates cinereus Hylobates cinereus Average u f 7 Hylobatcs ciner. Orang utaii Orang utaii Orang-utan Orang-litan Average of 2 adult orang-utaii Chimpanzee Cliimpauzce Cliimpanzee Average of 3 chimpanzees Negro ( 3 7 years) Negro (41 years) Negro (31 years) Average o f 3 Negroes w. f. f. m. f . R. f . w.f. w.f. w.f. w. f . w.f. w. f. I\*.f. IV. I\’. f. w. f. 1v. f . IT. f . w.f. 17. f . m. f. 71’. f . w.f . 1v. p. m. f. w.f. n-.f. m. f. IT. f . IT. f. f. m. f . TT. w.f. c. p. c . 13. e . p. e . p. f. f. f. 5.45 5.6; 5.67 6.12 6.12 6.12 6.36 6.35 6.35 6.58 6.58 7.03 3.6 3.9 3.4 3.4 3.2 4.3 4.9 3.7 3.7 0.039 0.0.53 0.060 0.059 0.064 0.056 0.053 0.050 0.068 0.074 0.056 0.053 3.4 6.30 3.6 o.n.5.9 14.06 20.42 80.42 20.42 20.57 20.87 23.14 23.59 97.47 5.2 7.32 16.0 11.8 9.6 14.6 18.0 13.2 4.98 4.98 4.98 5.44 5.90 6.12 6.35 5.5d 29.95 34.50 72.18 77.10 2.9 3.0 6.1 6.1 5.4 5.2 74.64 85.3 40.20 43.77 49.05 119.5 108.0 129.0 0.037 (1.035 0.078 0.058 0.046 0.070 0.078 0.056 0.057 0.058 0.060 0.122 0.112 0.091 0.085 0.058 0.084 0.097 0.068 0.045 0.050 0.048 0.297 0.247 0.263 44.34 118.R 0.269 34.89 66.30 69.42 43.0 51.0 36.5 0.078 0.077 0.081 6.7.,511 50.d 0.07.9 After €Irdli?ka ( ’25). a One testis undescended and vestigcal. Juvenile ( C and N3 not yet eruptcd). w.,wild; c., captive; f., fresh; p., preserved (embalincd). 389 3.2 3.0 11.3 3.73 4.6 29.0 23.4 32.4 ,382 390 ADOLPH H. SCHULTZ The macaques and baboons (Macaea and Papio ) represent the subfamily ('ercopitliecinae and the langurs and proboscis monkeys (Pygathrix and Nasalis) the subfamily Semiiopithecinae of the entire family of Old World monlieys. Last in the table are the higher primates : Gibbon (Hylobates), orang-ntan, chimpanzee, and Ilian. Tnfortunately it was impossible to obtain actual weights 011adult male gorillas. Based upon palpation of the scrotiim in several preserved bodies of adult gorillas, the author does not hesitate t o state that the testes of this aiithropoid ape are comparatively small and appear to have a relative weight considerably below that in man. The ratio of testicular. weight to body weight arnonnts to more than 0.1% i n a11 the New Worlcl monkeys examined. I t is smallest in the night monkey (,4otns) and the spider monkey (Ateles) and largest in the marmoset (Oedipomidas) and the howling monkey (Blouatta). One of the latter was collected and embalmed by the writer in Nicaragua, the other sere11 come from Panama and were weighed fresh, yet their ratios appear fully comparable. The relative weight of the testes differs to a very marked extent in the two subfamilies of Old World monkeys. I n the five species of macaques the relative weight of the testes fluctuates beween 0.46 and 0.92 and the baboon lias a corresponding valne of 0.28. I n langnrs, 011 the other hand, the relative weight of the testes shows very much smaller averagcs, i.e., 0.08 in one species and 0.06 in another, the latter average occnrring also in the closely allied proboscis monkey. Thus it is found that a rhesus monkey, weighing riot quite 10 Bg., has testes weighing 74 gm., whereas proboscis monkeys with an average body weight of over 20 kg. have an average testiciilar weight of only 11.9 gm. Among the higher primates the chimpanzee has undoubtedly the proportionately heaviest testes. Adult orang-utans possess a smaller relative testicular weight than even the langurs. This relative weight averages about the same in gibbons as in man. The value for the latter agrees very closely with that ITEIGHT O F TESTES IK PBI&IATES 391 giwn by Vicrordt (1688, p. 17), who lists 0.08 as relative weight of tlie testes in adnlt man (presumably n'hite). It is rather surprising t o fiiid that, e.g., a bonnet macaque weigliing only 8.4 kg. has slightly heavier testes (57.6 gm.) than a Negro weighing 69.4 kg. whose testes tip the scale at 56.5 gm. I n other words, per kilogram of body weight the former has 6.9 gm. of testicdar tissue, idicreas the latter only 0.8 gm. or eight and a half times less. It is difficult t o suggest any reasons f o r these midc discrepancies in thc rclative weight of the testes among different primates. Tliep are iiot connected with any seasonal changes in the life of the monkeys; at least the author's field notes and the distribution of the ages of all the animals collected give 110 illdieation of any breeding season among the Old World primates. It w a s attempted t o compare the relative size of the testes with the physiological age (as indicated by the state of attrition of the teeth) of tlie specimens in ilie series of macaques and of langurs, but it was soon apparent that there exists no correlation whatsoever between these two factors among adult animals.2 Tt seems possible, finally, that testes of widely differing relative size may contain the various tissues in very different proportions. Some of the testes, therefore, were sectioned and stained f o r microscopic study. The author is greatly indebted to his colleague, Dr. I. Gersli, for help in this undertaking. Sample sections of the testes were drawn thirty times eiilarged with the camera lucida on heavy paper of uniform thickness. The parts representing ( A ) the tubules or the sex-cell producing glandular tissue were carefully cut out and these as well as bhe remaining parts, representing (B) the reticular and collagenous connective tissue, interstitial glandular tissne, blood vessels and nerves, were weighed separately with the following results : " I t is interesting to note t h a t the two juveiiilc o r a n g u t a n s i n the table possess relatively larger testes t h a n the two full grown orang utans. On the other hand, small series of juvenile macaques and gibbons showed much smaller relative testieular weights than the corresponding series of adults. 392 ADOLPH H. SCHRTJLTZ A PRIMATE (TUBULBB) g m. Langur Gibbon Negro Chimpnnzee Baboon Macaque 0.06 0.06 0.08 0.26 0.28 0.72 B (FONNBCTlVE TISSUS) A+B m. m. 4.51 4.49 4.52 4.50 4.49 4.49 2.15 2.30 2.54 3.17 3.31 2.36 3.08 1.41 2.19 1.98 1.33 1.18 Contrary t o what might have been expected, it is foiind that the primates with relatively large testes (chimpanzee, baboon and macaque) have a considerably greater proportion of sexcell producing glandular tissue and a smaller proportion of connective tissue than have the primates (langur, gibbon and man) with comparatively small testes. On the assumption that the sample sections which have been analyzed are representative of the entire testes, it can be calculated that per kilogram of body weight the langur possesses 0.29 gm. of tubular tissue (A) and 0.31 gm. of connective tissue (B), whereas the macaque 4.9 gm. of tubular tissue and 2.3 gm. of connective tissue, This means that per unit of body weight the macaque has seventeen times more of the sex-cell prodncing glandular tissue than the langur. Two of the adult, wild-shot primates in the table are marked as having one testis undescended and vestigeal. A few notes on this rare condition of unilateral cryptorchism are added here since it appears to have some connection with the size of the testes. I n one of the adult proboscis monkeys only the riglit testis, weighing 7.0 gm., had descended in the scrotum and the left had been retained in the abdomen, weighing only 0.2 gm. This is unquestionably an abnormal condition and identical with the finding in an adult gibbon (Hylobates cinereus) from Borneo. I n this ape the right testis was i n the scrotum and the left way up in the abdomen; the former testis weighed 3.4 gm. and the latter only 0.3 gm. Among the male gibbons collected by the author in Asia there are two further cases of a very similar nature, thongh they appertain to juveniles. I n a HyIobates cinereus, weighing 3.18 kg., in WEIGHT O F TESTES I N P R I M A T E S 393 which the permanent canines and third molars had not yet erupted only the left testis of normal size was in the scrotum while the right, of excecdingly small size, was found in the abdomen. Exactly the same condition occurred in a Hylobates lar, wcighing 3.40 kg. and with all permanent teeth, except the third molars. This unilateral cryptorchism was found in three out of sixty-two wild gibbons (twelve juveniles and fifty adults), or in 5% of the cases. The two cases in jux-eniles are not caused merely by a slightly retarded descent of one testis, as is evident from thc vestigeal nature o f the testis in the abdomen and also from the following observations on the normal time of descent of the testes in gibbons, based upon the author's field notes of last year : HYMRATXS BODY WBIGIIT DhNPlTTON TESTES IN kg. lar lar lar lar cinereus lar cinereus cinereus lar lar ein wells cinereus lar la r lar 0.45 0.68 0.68 0.68 0.91 1.36 1.36 1.59 2.04 3.15 3.40 3.40 3.63 3.83 4.08 Inc~ompletcmilk dentition Complete niilk dentition Complete milk dentition Complete milk dentition Complete milk deiititioii Tncomplete pennanrnt dentition lncomplete permanent dentition Tncomplete permanent dcntitioii Incomplete permanent dentition Incomplete permanent dentitioii Ineorriplete perinanent dentition Incomplete permanent dentition Incomplete permanent dentition Incomplete permanent dentition Incomplete lxrmanent dentition Scrotum Abdomen Scrotum Scrotum Scrotum Abdomen Scrotum Scrotum Rcrotuni Scrotum Srrotum ScrotuKtl Scrotum Swot 11m Scrotum NOTE: Adult male Hylobates Par hare a n average body weight of 5.7 kg. a i d adult male Hllobates cinerens one of 5.5 kg. These two spccimens were living i n captivity when examined, all the other specimens, exnmined fresh immediately after death. gibbons listed are ~ i l shot d I n his paper on the genitalia of primates Wislocki ( ' 3 6 ) lias listed one juvenile Hylohates lar and two juvenile H. cinereus in all of which the icstes had dcscended in the scrotum. It seems safe to conclude, therefore, tliat at least in these two species of gibbons the testes descend normally during in- 394 ADOLPH H. SCHULTZ fantile life, ie., before any permanent tpeth make their ~ p pearanc c. SUMMARY The weight of the body and of the testes and the percentage relation between the two is recorded for a total of eiglltly adult and two juvenile simian primates. This relative weight of the testes fluctuates between 0.1 and 0.4 among American monkeys. I n monkeys of the Old World the testes are proportionately much heavier in the suhfamilj- Cercopithecinae The relative testiealar than in the subfamily Scinno~~itlrecinae. weight varies among five species of macaques between 0.46 and 0.92, whereas in langurs it averages oiily 0.06 and 0.08 in different series. Among higher. primates this ratio amounts to 0.05 in orang-utans, 0.08 in gibbons and in man, and 0.27 i n chimpanzees. Such striking differences i n the relative size of the testes are best demonstrated by the example of a bonnet macaque, weighing 8 kg., which has slightly heavier testes than a Negro weighing 69 kg. Small testes, relative to hodj7 size, coiitaiii a proportionately miwh smaller amount of tubules and a much larger amount of conncctive tissue than relatively large testes. It is calculated that, with equal body weight, a macaque, e g . , has seventeen times more sex-cell producing glandular tissue than has a langur. In one proboscis monkey and in three gibbons there exists unilateral crpptorchism, i.e., one testis was retained i n the abdomen and is of diminutive size and the other had descended in the scrotum and is of usual size. Normally the testes of these gibbons descend during infantile life. LITERATURE CITED A. 1925 Weight of the brain and of the internal organs in American monkeys. Am. J. Phys. Anthrop., vol. 8 , pp. 201-211. VImomr, H. 1888 Anatomischr, physiologiaehe nnd pliyikalischc Daten uud Tabcllen zum Gebraiiche fiir Mediziiier. Jeiia. WISLOCKI, G. B. 1936 The erterual genitalia of thc simian primates. Human Biol., vol. 8, pp. 309-347. HRDIJCK-4, Thc only juvenile Hylobates 1ar viith both testes still in the abdomen has merely its first pcrmaiirnt molars besides thc complete milk delitition and appears to be a n exception, though Wislocki records undescended testes in three juvenile gibbons of other species (H. concolor and 13. leucogenys).