Florence R. Sabiii 



385 



peripheral sinus filled with blood. It looks exactl}^ like the follicles 

 marked h in Fig. 16, except that the sinus is filled with blood. The 

 next stage looks like the nodes marked c in the same figure, while a tliird 

 stage shows an increase in the lymphoid tissue. 



The hfemohmiph node thus parallels the stages in development of the 

 other nodes, except that its sinuses from the beginning belong to the 

 blood-vessels rather than to the lymph vessels. In the lymphatic nodes 

 the sinuses are made of the modified veins called lymphatics, while in 

 the hffiuiolymph node they are made of the veins themselves. The espe- 



Ar-terx| 



Fig. 17. Lymph follicle without a peripheral sinus, found in the edge of a 

 lymph duct in the lung of an adult pig. X 66. 



cial point in the development of the nodes which is not yet clear is the 

 relation of the veins which make the sinuses to the rest of the blood- 

 vessels of the node. 



In all of the specimens of the hasmolymph nodes as far as they have 

 been studied, that is in pigs up to 3 weeks old, the venous or sinus 

 portion of the node predominates over the lymphoid element. The 

 nodes show both the true sinus and the plexus formation observed in 

 lymphatic nodes, but the developed sinus is mucli more limited in 

 amount. This is also true in all of the htemolymph nodes I have seen 

 from the adult pig. 'They consist of three elements, the lymphoid masses 

 surrounded by true sinuses, and a considerable amount of a venous 



