12 MASS. EXPERIMENT STATION BULLETIN 331 



Taule 8. — The Effect of Castration upon the Development and 



Maintenance of Temperature Sensitivity in the Tunica Dartos 



Muscle of the Ram. 



At Cast 

 Animal 



A 



B 



C 

 D 

 E 

 F 

 G 



An examination of the figures reveals two interesting points: (a) If a ram 

 was castrated before the tunica dartos developed a marked sensitivity to tem- 

 perature changes, this sensitivity did not develop later; and (b) if a ram was 

 castrated after the tunica dartos had developed a sensitivity to temperature 

 changes, this sensitivity tended to be lost. Both of these facts indicate that the 

 tunica dartos depends upon the presence of the testes for normal development 

 and maintenance of its temperature-regulating function. 



Testicular Hormone Injections 



Seven ram lambs were injected with testicular hormone ("Hombreol"), the 

 dosage varying from 20 to 100 cock units. At the end of the injection periods 

 (7 to 18 days) these lambs ranged in age from 41 to 56 days. Strips of the 

 tunica dartos were taken and subjected to temperature changes as has been 

 described earlier in this bulletin. When compared to normal rams four of these 

 showed some precocious development of the tunica dartos muscle. These rams 

 ranged in age from 41 to 54 days when the strip of tissue was excised and had 

 received from 60 to 100 cock units of 'Hombreol' over a 10 to 13 day period. 

 The amount of activity was not equal to that observed in rams of 84 days of 

 age and over, but some precocious development was obvious. 



Weight of the Testes 



The above observations indicate that the testicular hormone, or one fraction 

 of it, is concerned with the development of the tunica dartos. It seemed possible 

 that the weight of the testes might also have some effect on the development of 

 this muscle. To check this, two ram lambs were castrated and the testes re- 

 placed by steel balls. The tunica dartos of one of these rams had not developed 

 a reaction to temperature changes at the time of castration (28 days) and did 

 not develop it later. The second ram had developed some reaction when cas- 

 trated at 62 days but lost this sensitivity following the replacement of the 

 testes by steel balls. 



Results with these two animals indicate that weight of the testes is not a 

 factor in the development of the tunica dartos. 



