lvjMphatic organs 



177 



and placed for twenty-four hours in fornialin-MuUcr's fluid, llieii hardened in 

 alcohol. Sections are cut through thr hikun, stained with haematoxylin-eosin or 

 with hsematoxylin-picro-acid-fuchsin and mounted in balsam. Near the centre 

 of the chain are usually found nodes in which the lymph sinuses arc properly dis- 

 tended. The most proximal nodes are apt to be overdistendcd, but for this very 

 reason are often excellent for the study of the reticular tissue from which most 

 of the cells have been washed out, especially in the medulla. 



(3) Human lymph nodes may be treated by either of the above methods. 

 Owing to the coalescence of their cortical nodules their structure is not so easily 

 demonstrated as that of the lymph nodes of lower animals. 



Haemolymph Nodes 



These are lymphoid structures which closely resemble ordinary 

 lymph nodes, but with the essential difference that their sinuses are 

 hlood sinuses instead of lymph sinuses. 



Fig. 103. — Section through Human Haemolymph Node, including Hilum, showing cap- 

 sule, trabeculse, sinuses filled with blood, and Ij^mph nodules. (VVarthin.) 



I Each node is surrounded by a capsule of varying thickness, com- 

 posed of fibro-elastic' tissue and smooth muscle cells. From the cap- 

 sule traheculoe of the same structure pass down into the node, forming 

 its framework (Fig. 103) . Beneath the capsule is a hlood sinus, which 

 may be' broad or narrow, and usually completely surrounds the node. 

 Less commonly the sinus is interrupted by lymphoid tissue extending 



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