96 ELEMENTS OF HISTOLOGY. [Chap. XH. 



circumference of the follicles of the tonsils, pharynx, 

 intestine, bronchi, &c., is surrounded by a lymph 

 sinus leading into a lymphatic vessel. The lymphatic 

 vessels and lymph sinuses in the neighbourhood of lym- 

 phatic follicles or of diffuse adenoid tissue are almost 

 always found to contain numerous lymph corpuscles, 

 thus indicating that these are produced by the adenoid 

 tissue and absorbed by the lymphatics. 



127. The Tliymus gland consists of a frame- 

 work and the gland substance. The former is fibrous 

 connective tissue arranged as an outer capsule, and 

 in connection with it are septa and trabeculae passing 

 into the gland and subdividing it into lobes and 

 lobules, which latter are again subdivided into the 

 follicles (Fig. 5 9 A). The follicles are very irregular 

 in shape, most of them being oblong or cylindrical 

 streaks of adenoid tissue. Near the capsule they are 

 well denned from one another, and present a poly- 

 gonal outline ; farther inwards they are more or less 

 fused. Each shows a central transparent medulla 

 and a peripheral less transparent cortex (Watney). 

 At the places where two follicles are fused with one 

 another the medulla of both is continuous. The matrix 

 is adenoid reticulum, the fibres of the medullary part 

 being coarser and shorter, those of the cortical portion 

 of the follicle finer and longer. The meshes of the 

 of the reticulum in the cortical part of the follicles are 

 filled with the same lymph-corpuscles as occur in the 

 adenoid tissue of other organs, but in the medullary 

 part they are fewer, and the meshes are more or less 

 completely occupied by the enlarged but transparent 

 endotheloid plates. These conditions cause the greater 

 transparency of the medulla. In some places the 

 endotheloid cells are granular, and include more than 

 one nucleus ; some are even multinucleated giant cells. 



128. There occur in the medulla of the follicles, 

 larger or smaller, more or less concentrically-arranged 



