John Bruce MacCallum 



255 



any 



case be forced through the entire length of the tubules. Usually 



only an occasional tubule near the middle 

 of the gland, and in the male the fine 

 tubules at the extreme anterior end are 

 filled with the colored solution. An in- 

 jection of the gland in the female at this 

 stage is shown in Fig. 10. It will be no- 

 ticed that both the WoMan and Miiller- 

 ian ducts are injected. The organ is 

 drawn from its lateral surface to show the 

 extent to which the Wolffian tubules have 

 been injected. The tubules are by no 

 means so alnmdant as in younger emljryos. 

 The glomeruli are still present in consid- 

 erable nimibers. The interstitial tissue is 

 relatively greater in amount than in ear- 

 lier stages. Degenerating tubules in such 

 a gland are shown in section in Fig. 11. 

 In the upper tubule the lumen is seen to 

 be partially filled with epithelial cells, 

 while in the lower tubule the lumen is 

 almost obliterated. 



In embryos 130 mm. long the tubules 

 cannot be injected at all in the posterior 

 (urinary) part of the 

 Wolffian body. In 



the female the fluid runs up in the Miillerian duct 



and flows into the body ca^dty. In the male there 



is a complete injection of the anterior (sexual) 



part of the organ, ('. e., the epididymis. In pigs 1-10 



mm. long it requires considerable pressure to force 



fluid into the Wolffian duct. On entering, how- 

 ever, it runs up to the anterior end and flows out as 



before into the tubules near the head of the testis. 



In embryos 1-15 mm. long the injection fluid fills 



a considerable mass of tubules representing the 



head of the epididymis. In the female it requires 



onlv very little pressure to cause the fluid to flow through the Miillerian 



duct to the body cavity. Here the Wolffian duct can no longer be 



injected. 



Fro. 10. Injection of Wolffian and 

 Miillerian ducts in a pig^'s embryo 

 120 mm. long-. O.. ovary ; M., Miil- 

 lerian duct; AV., Wolffian duct; A.. 

 allantois; K., Ividney. The organ is 

 viewed from the side. 





'>^e^ 



Fig. 11. Section show- 

 ing obliteration of tu- 

 bules in a pig's embryo 

 130 mm. long. 



