CASTRATION— ANATOMY. 197 



Owing to the essentially different methods of procedure in male and 

 female animals, castration will be treated of separately in each sex. 



Castration of Male Animals. 



Experience shows that male animals are best castrated young. 

 Many of the advantages claimed for operation, such as the change 

 in bodily form, are lost when it is too long deferred. 



Excluding the first few weeks of life, most domesticated animals 

 undergo operation during the first }-ear. The horse is an exception, 

 because in it the testicles lie within the inguinal canal during 

 part of the first year, towards the end of which they usually 

 descend into the scrotum, and so become readily accessible. More- 

 over, horses castrated during the first year often assume a female 

 type, whilst those in which operation is deferred develop to a 

 greater extent. Nevertheless, animals can be, and racehorses some- 

 times are, castrated before the expiration of the first year in 

 order to hasten the advent of their period of usefulness. The 

 operation then resembles that on inguinal cryptorchids. 



Anatomy. — The testicles, removal or disabling of which is aimed 

 at in castration, are suspended in the scrotum b}^ means of the 

 testicular cords. The scrotum and the structures it encloses may be 

 divided from without inwards into the following layers : 



1. The outer skin. This is soft and thin, usually hairless, in the 

 horse black and shining ; it is very extensible, and is directly con- 

 tinuous with the common integument. In ruminants the scrotum 

 shows a distinct neck ; the skin covering it is light coloured, and 

 exhibits little hair. In swine the scrotum, which is broad and smooth, 

 lies between the hind quarters, close under the anus ; in carnivora it is 

 somewhat further forward. 



2. Beneath and intimately connected with the skin is the tunica 

 dartos, which consists of a modified subcutis abundantly supplied with 

 unstriated muscular fibres, elastic and white fibrous tissue. Above 

 it is connected with the yellow elastic abdominal tunic, while a 

 prolongation of the tunica dartos, the septum scroti, serves to divide 

 the scrotum into two equal portions. Strictly speaking, the skin and 

 tunica dartos together form the scrotum. 



3. The spermatic fascia, continuous with the tendon of the external 

 oblique muscleT 



4. The cremasteric fascia, continuous with the internal oblique 

 muscle. 



5. The infundibuliform fascia, continuous with the transversalis 

 muscle. 



6. The tunica v.aginalis reflexa, a layer of serous membrane con- 

 tinuous with the abdominal peritoneum. 



