90 PLAIN FACTS FOR OLD AND YOUNG 



or testicle, of wliicli eacli male possesses two. They 

 are elastic, glandular bodies, and are formed within 

 the cavity of the abdomen, near the kidneys, but usually 

 pass out of the abdominal cavity, and descend to their 

 permanent position before birth. The opening in the 

 abdominal wall is usually comi^letely closed in a short 

 time; but occasionally it remains open, giving rise to 

 hernia, an accident in which a loop of intestine fol- 

 lows the testicle down into the scrotum, either com- 

 pletely or partially. In a few animals, as in the por- 

 cupine, the opening is never fully closed, and the testis 

 remains in the cavity of the body most of the time, 

 passing out only at certain periods. There are occa- 

 sional cases of human beings in which the testes have 

 never descended from their place in the abdominal 

 cavity, giving the individuals the appearance of 

 eunuchs. 



When the testicles are thus retained, they are usu- 

 ally imperfectly developed, and consequently the per- 

 son is likely to be sterile. This is not always the case, 

 however, and hence it occurs that men who appar- 

 ently have no testicles, become the fathers of children. 



In the whale, the elephant, and the seal, the testicles 

 remain permanently within the abdominal cavity, 

 though in most animals they are supported outside the 

 body in a sac, as in man. 



The left testicle is sometimes a little smaller than 

 the right, and commonly hangs a little lower. The 

 testicles are connected with the urinary passage by 

 means of two ducts, which terminate near the base of 

 the bladder. 



Spermatozoa.— A single spermatozoon somewhat 

 resembles a tadi3ole in appearance, having, however, 

 a much longer tail in proportion to the size of the body. 



