236 PRACTICAL HISTOLOGY. [XX. 



cat. For the germ-centres harden a small gland in Flemming's fluid 

 and stain with safranm. Make sections including both poles of the 

 gland and the hiluin. Stain them with logwood and then with 

 eosin. Mount in balsam. 



(a.) (L) Observe the capsule (fig. 222, c) surrounding the gland, 

 and sending at fairly regular intervals septa or trabeculse into the 

 substance of the gland. The trabeculae and capsule are stained by 

 the eosin. The trabeculae are flattened in the outer part or 

 cortex, and divide ifc into compartments follicles or alveoli (F). 

 The trabeculae are continued into the central part or medulla, 

 where they form a network of smaller, branched, more rounded 

 trabeculse. 



(b.) The compartments in the cortex are nearly filled by leuco- 

 cytes lying in a meshwork of adenoid tissue constituting the 

 follicles (cortical nodules) of the cortex (fig. 222, F). Between 

 the trabeculae of the medulla the leucocytes are equally abundant. 

 Owing, however, to the arrangement of the trabeculse, they form 

 medullary cords, but everywhere the adenoid tissue is continuous 

 throughout the gland. 



(c.) The lymph channels (s) exist between the capsule and the 

 follicles, and between the trabeculae and the lymphoid tissue of the 

 cortex and medulla (figs, 222, 223). They form an anastomosing 

 system of paths or channels throughout the gland, and are traversed, 

 by a fine network of coarse adenoid tissue with comparatively few 

 leucocytes in its meshes (fig. 223). 



(d.) (H) The capsule and trabeculae, chiefly composed of connec- 

 tive tissue, and in some animals (ox) with smooth muscular fibres. 

 Continuous with its under surface is a delicate network of adenoid 

 tissue, which stretches across the lymph channel to the follicle, 

 where it becomes continuous with the adenoid tissue supporting 

 the leucocytes (fig. 223). Between the trabeculae and the medul- 

 lary cords in the cortex similar lymph paths with an adenoid net- 

 work. 



(e.) The follicles and medullary cords, everywhere crowded with 

 leucocytes. 



2. Adenoid Reticulum. (i.) As this is largely obscured by the 

 presence of the leucocytes, these must be got rid of. This is readily 

 done by making sections of the lymph gland of an ox, hardened for 

 two or three days in 5 per cent, ammonium bichromate, and then 

 shaking the sections in a test-tube containing water, or the leuco- 

 cytes may be "pencilled " out by a camel's-hair pencil. 



(ii.) A better method, perhaps, is to inject by the puncture 

 method (p. 237) a J per cent, solution of silver nitrate into the 

 lymph gland of an ox. The fluid being driven in forcibly, causes 

 an artificial oedema and forces the parts asunder. Harden in 



