DEVELOPMENT OF TESTES AND SCROTUM 7 



Table 4. — Gains Made by Boar Pigs on High and Low Planes of 



Nutrition 



Age at Gain from Weaning to Time of Castration 



Castration (Pounds) 



(Days) 



High Nutrition Low Nutrition 



84 19 14 



105 70 16 



126 95 36 



147 140 56 



168 71 



At the time of castration measurements were taken of the volume of the 

 testes (with epididymis removed) and of the diameter of the tubules. These 

 figures are given in Table 5 and show that the low plane of nutrition resulted 

 in a marked slowing up of the growth of the testes in total size as well as in the 

 diameter of the seminiferous tubules. 



Table 5. — Effect of Low Nutrition on Volume of Testes and Diameter 

 of Seminiferous Tubules 



Age at Volume of Testes (c.c.) Diameter of Tubules 



Castration (Both Testes) (Micra) 



(Days) 



High Nutrition Low Nutrition High Nutrition Low Nutrition 



84 12 10 59.3 55.4 



105 107 13 83.8 58.6 



126 220 83 139.9 122.5 



147 300 82 165.7 99.3 



168 — 68 96.7 



The development of the germinal epithelium was also retarded by low nutri- 

 tion when compared with litter-mate controls, with one exception. The ex- 

 ception was the 126-day stage which showed a fully developed epithelium with 

 numerous spermatozoa. The other ages examined showed little development 

 of the epithelium. At 84 and 105 days only spermatogonia and a few spermato- 

 cytes were present. At 147 days secondary spermatocytes had appeared; but 

 at 168 days, the oldest stage examined, only spermatogonia and a few primary 

 spermatocytes were present. 



Photomicrographs of sections from four of the boars on a low plane of 

 nutrition are shown in Figures 12 to 15, where they may be compared with 

 controls shown in Figures 9 to 11. 



DEVELOPMENT OF THE TUNICA DARTOS 



Materials for the study of the tunica dartos muscle were obtained from all 

 the animals from which testes were obtained. The development of the tunica 

 dartos was studied in two ways. At the time of castration two strips of tissue 

 were taken along the vertical axis of the scrotal wall. One was fixed and pre- 

 pared for histological examination and the other was mounted in aerated 

 Ringer's solution, attached to a muscle lever, and subjected to temperature 

 changes. Starting at about 37°C. the temperature was gradually lowered to 20°, 

 held there for five minutes, and then gradually returned to approximately 37°. 

 The reactions of the strips to these temperature changes were recorded on a 

 kymograph. 



