238 



THE LYMPHATIC SYSTEM 



The pulp spaces are broad channels, which are occupied by a reticu- 

 lum whose meshes are partially filled with lymphocytes. They are 

 bounded by a layer of endothelioid cells which everywhere incloses the 



denser lymph cords. The function of 

 these cords would seem to be comparable 

 to that of the peripheral lymph nodules. 

 The pulp spaces are open toward the 

 cortex, whence they receive the afferent 

 lymph after it has percolated through the 

 nodules, but toward the hilum the spaces 

 are continued into the efferent radicles of 

 the lymph vessels which, in the connective 

 tissue of this part, unite into larger 

 trunks, and finally form several efferent 

 lymph vessels of considerable size. 



The reticulum of the lymph gland is 

 a close-meshed network of interlacing fi- 

 brillar bundles, which are here and there 

 clasped by flattened endothelioid connec- 

 tive tissue cells. Eeticulum is but poorly 

 stained with either acid or basic dyes, is 

 destroyed by acids and bases, but is not 

 digested by pancreatin. After prolonged 

 action of Weigert's specific stain for elas- 

 tic tissue it is but slightly colored. 



Lymph Cells. The great majority of 

 these cells are of the small mononuclear 

 or lymphocyte type. Large mononuclear 

 cells with a considerable cytoplasmic body 

 are also very numerous. Polymorphonu- 

 clear neutrophil leukocytes, though of 

 frequent occurrence, are less abundant 

 than the previous varieties. Eosinophil 

 cells are present in small numbers, and 

 large basophilic mast-cells are occasionally seen, though according to 

 Carlier (Jour. Anat. and Physiol., 1893) they are mostly confined to 

 the connective tissue. Drummond (Jour. Anat. and Physiol., 11M)0) 

 also found large multinuclear giant cells, megakaryocytes, similar to 

 those of the bone-marrow; these were, however, very rare. 



Many of these cells, after proper fixation, show mitotic figures. This 



FIG. 245. DIAGRAM OF THE 

 BLOOD-VESSELS OF A LYMPH 

 NODE. 



A composite section of three 

 follicles and the medullary cords 

 of a mesenteric lymphatic node 

 of the dog. A, artery; B, medul- 

 lary artery; C, follicular vein; E, 

 artery going to the capsule; F, 

 capillaries in the periphery of a 

 cord; G, medullary vein; H, fol- 

 licular artery; I, arterial capil- 

 laries in a follicle; J, vein from 

 capsule; K, cord; L, trabecula; 

 F, vein. X 501. (After Calvert.) 



