MAMMALIAN SEXUAL CHARACTERS 149 



the ground after being hurled upwards and forwards, 

 the abdominal organs have acquired a rapid move- 

 ment downwards and forwards; when the body 

 reaches the ground its movement is stopped 

 suddenly, while the abdominal organs continue to 

 move. The testes therefore are violently jerked 

 downwards away from their attachments and at the 

 same time forward. The check to the forward 

 movement, however, is momentary, while the body is 

 immediately thrown again upwards and forwards, 

 which by the law of inertia means that the testes are 

 thrown still more downwards and backwards. There 

 is no reason to suppose, as Dr. Woodland suggests, 

 that any rupture of the mesorchium was the usual 

 result of these strains, but a constant pull or tension 

 was caused in the direction in which the testes 

 actually move during development. On this theory 

 we have to consider (1) how such strains could cause 

 a shifting of the peritoneal attachment, (2) why the 

 testes should be supposed to be particularly affected 

 more than other abdominal organs. The answer 

 to the first question is that the strains would cause 

 a growth of the connecting membrane (mesorchium) 

 at the posterior end, accompanied by an absorption of 

 it at the anterior end. The answer to the second 

 question is that the testes are at once the most 

 compact and heaviest organs in the abdomen, and 

 at the same time the most loosely attached. The 

 latter statement does not apply to the mesonephros 

 or epididymis which has moved with the testis, but 

 the latter cannot function without the former, and 

 it may be supposed that the close attachment of the 

 epididymis to the testis had come about in the early 

 Mammalia before the change of position was evolved. 



