24 ANIMAL CASTRATION 



tunica vaginalis communis, and tunica vaginalis 

 propria. The dartos is derived from the abdominal 

 tunic; the scrotal fascia is contributed by the oblique 

 abdominal muscles ; the tunica vaginalis communis is 

 a continuation of the parietal peritoneum; and the 

 tunica vaginalis propria is the mesorchium of the 

 fetus. These coverings are not pi'oper to the testicle, 

 but, strictly speaking, are coverings usually considered 

 as forming the scrotum. 



The proper covering oF the testicle is the fibrous, 

 inelastic, closely-investing tunica albuginea, which is 

 not directly attached even lo the tunica vaginalis 

 propria. In the immediate region of the sci'otum there 

 is to be found in some cases in colts an alniormal de- 

 ^•elopmcnt of branches ol; the external pudic veins 

 forming plexuses. This is common in cr>-ptorchids. 



There is much difference in the comparative size of 

 the testicles in the various domestic animals. Bulls, 

 sheep and goats have comparatively large testicles, 

 which are supported in the sub-pubic region in a pen- 

 dent manner, exposing these glands to injury from 

 ballotment between the thighs or from actual vio- 

 lence in many other ways. The testicles of the boar 

 are comparatively large but closely invested by the 

 scrotum, and situated in the external perineal region 

 in such manner that thej^ are well protected. In the 

 horse the testicles are comparatively smaller than are 

 those of tlie animals aforementioned, suppoiied I'athcr 

 more closely to the body in tlie sub-pubic I'egion and 

 ordinarily iTot sub.iect to injury except fi'om chafing, 

 this occurring more often in light hai'iicss horses put 

 at fast work. 



