XIV 



THE LYMPH 



529 



and break up into a capillary network which subsequently reforms 

 into one or more venules. Round the nodule there is a space or 

 lymphatic sinu.s tilled with lymph, interrupted by afferent and 

 efferent blood-vessels and filaments of connective tissue, which 

 unite the tissue of the adenoid serosa with the surrounding 

 connective tissue. The lymph sinus and the blood-vessels and 

 connective-tissue bridges are clothed with epithelioid plates, as 

 shown by the silver nitrate reaction. 



The leucocytes implanted in the adenoid rete are usually 

 smaller than those of the blood, owing to the paucity of protoplasm 

 around the nucleus. Many of them, lying within the central 



' 



PIG. 248. Solitary follicle from large intestine of mail. (Bulmi.) cp, Intestinal epithelium ; 

 gl, Lieberkuhn's crypt ; eg, germinal centre ; sm, sub-mucous tissue. 



mass of the follicle, are in the stage of niitotic division, so that 

 Flemming gave the name of centrum germinativum to the mid- 

 point of the follicle, at which there is a continuous multiplication 

 of leucocytes. In proportion as new leucocytes are formed at the 

 centre, the adult leucocytes which lie at the peripheral part of 

 the follicle are driven towards the lymphatic sinus, where they 

 are caught up in the general lymph current. The vis a tergo that 

 drives them out of the meshes of the adenoid rete is no doubt 

 due to the lymph which transudes from the network of the 

 blood capillaries in the follicle, and increases the tissue tension. 

 The lymph which is thus formed, while it serves as food for the 

 leucocytes, is modified by the products of their metabolism. It is 

 probable that a proportion of these products passes by diffusion 

 into the interior of the blood - vessels, so that the blood, on 

 VOL. i 2 M 



