HUMAN TESTIS AND EPIDIDYMIS 397 



recti often run for some distance before joining the seminiferous 

 tubules. Frequently two testis cords anastomose just before 

 joining a rete cord; on the other hand, one testis cord maybe 

 connected with several rete cords. 



In regard to the age at which the testis and rete cords join, I 

 find such differences between my findings in man and Allen's 

 in pig and rabbit that they seem worthy of note. Allen gives the 

 time of junction as about 13.0 cm. in the pig, and 21 days in the 

 rabbit ; in both cases the rete cords were already hollow before 

 joining. In man the development of this connection is much more 

 rapid, though there seem to be quite wide individual variations. 

 At 16.0 mm. there is no extension of the rete cords downward, 

 while at 23.0 mm. the cords have already grown past the upper 

 glomeruli into the mediastinum , and in embryos of 32.0 mm. have 

 already united with the testis cords. (In one embryo, H. E. C, 

 no. 819, of 19.0 mm., this union has taken place.) For some time 

 after joining, the rete cords in man remain solid, without lumen. 

 This precocious development of the rete cords in man may 

 be correlated with the small size and rapid degeneration of 

 the mesonephros, as compared with that of pig and rabbit. In 

 the sheep, another embryo with large mesonephros, the rete again 

 develops late; whereas in the cat, whose mesonephros is small, 

 the rete cords and testis cords have nearly joined at 24.0 mm. 

 (H. E. C, no. 467). 



By the end of the third month or the middle of the fourth the 

 rapid destruction of the testis network probably ceases, though 

 many connections may be severed much later; my preparations 

 give no information on this point. The cords become so long that 

 they are forced into convolutions, which increase progressively 

 till puberty; on the other hand the cords decrease in diameter, 

 becoming more and more slender until at seven months they are 

 of about one-half as great diameter as at three months. From 

 seven months on there is a gradual increase in calibre. This reduc- 

 tion in size may be due to a rearrangement of the cells to allow for 

 the rapid increase in length. The convolutions are in short, stiff 

 curves, which remain within a small area, condensing the connec- 

 tive tissue around them. It thus happens that different parts of 



