DEVELOPMENT AND FUNCTION OF HEMAL NODES 



399 



pendent of a plexus of vessels but may come into direct relation 

 to the vascular circulation. Independent capillaries and not 

 rarely a group of branching capillaries may come into relation 

 with the peri-nodal space as shown in figure 15 even before the 

 capsule has differentiated or during its differentiation. But 



Fig. 15 External section of a developing hemal node showing the relation 

 of the extra-nodal vessels to the snbcapsular blood space in the node shown in 

 figure 12. X 475. 



the peri-nodal space frequently is incomplete or ma}^ never 

 form, and the intra-nodal vessels frequently enter that portion 

 of the node which is still fully undifferentiated. The intra- 

 nodal circulation is formed by an artery and ^'ein which enter 

 the node by traversing the peri-nodal space which does not as 

 a rule communicate directly with them, a fact abundantly ob- 

 served in mature nodes of the sheep by Helly, Piltz and myself. 



