ORGANS OF GENERATION. 285 



muscular and mucous coats which compose all the hollow viscera. 

 It is retained in its place by the cellular membrane which connects 

 it with the lower walls of the pelvis, posteriorly by the urethra r 

 and by the folds of the peritoneum which are continued from it 

 to the sides of the pelvis, and are called the broad ligaments of the 

 bladder. 



THE ORGANS OF GENERATION, MALE AND FEMALE. 



THE MALE ORGANS OF GENERATION consist of the testes and 

 their ducts the vasa deferentia, the latter conveying the semen to 

 the urethra or to the vesiculae seminales, which are oval bags con- 

 nected with the upper surface of the neck of the bladder. Here 

 the seminal fluid is stored up for use, and when wanted is conveyed 

 into the vagina by means of the external organ or penis. The 

 anatomy of the testicles is that which mainly concerns the horse- 

 master, as they are generally removed by operation. They are 

 contained within the scrotum, which is externally composed of 

 skin wrinkled in the foal, but subsequently distended by the size 

 and weight of its contents. Beneath this is a layer of a pale yel- 

 lowish fibrous membrane called the dartos, which envelops the 

 testes and forms a separation between them. A thin coat of cellu- 

 lar membrane alone separates this from the double serous mem- 

 brane, the tunica vaginalis, which almost entirely envelops each 

 testis just as the pleura does the lung. In the early stages of foetal 

 life the testes are contained within the abdomen above the perito- 

 neum, but being attached to the scrotum by a thin muscle (the 

 cremaster) they are gradually dragged downwards through the 

 inguinal canal and each brings a double layer of peritoneum, which 

 continues its connection through life, so that fluid injected into 

 the cavity of the tunica vaginalis will flow into the peritoneum. 

 Hence inguinal hernia in the horse becomes scrotal in a very short 

 space of time, and rarely remains confined to the former position. 

 The testicles with their appendages, the vesiculae seminales, form 

 the semen by the usual process of secretion. They are of about 

 the size of a duck's egg, and besides their attachment by the re- 

 flexions of the tunica vaginalis to the scrotum, they have also the 

 spermatic cord which suspends them to the inguinal canal through 

 which it passes. This cord it is which is divided in castration, 

 and it is well to ascertain its component parts. They are, 1st. 

 The artery which supplies the testicles with blood, and is of con- 

 siderable size and tortuous in its course. 2d. The artery of the 

 cord, small and unimportant. 3d. The veins which accompany 

 these arteries. 4th. The nerves and absorbents, the division of 

 the former giving great pain and causing a slight shock to the 

 system. 5th. The vas deferens or duct carrying the semen to the 

 urethra, and possessing walls of such thickness that it feels like 



