448 



OTTO F. KAMPMEIER 





Fig. 20 Transverse section through the region of the future cisterna chyli 

 in a 21 mm. pig embryo (series 103, slide 39, section 12), X 200. 4, clear areas 

 representing the formation of lymphatic spaces around the posterior supracardinal 

 veno-lymphatics (6c); 13, aorta; 14, sympathetic nerve trunk. 



the features revealed in 21, 22 and 23 mm. embryos will give sup- 

 port to these observations. 



While the veno-lymphatics of the cisterna chyli region are anas- 

 tomosing extensively in the median line dorsal to the aorta, they 

 are beginning to lose their connections with the supracardinals of 

 both sides so that they come to exist in the form of a condensed 

 and abandoned multilocular venous plexus. Coincident with this 

 process, the mesenchyme located between the plexiform channels 



