20 Th. Lewis, 



finer strands, whicli terminate as the reticulum of the adenoid tissue 

 and sinuses. The character of the ''endothelium^' which lines the 

 capsule, the trabeculae, and lymphoid tissue, will be further discussed. 

 Having given the general relations of the three chief elements of the 

 gland, I proceed to a more detailed account of these constituent parts. 



The capsule and trabeculae. A capsule is alwajî's present, in 

 certain cases consisting of both fibrous and serous layers, as in the 

 case of the spleen and many lymphatic glands. It varies in thickness 

 with the size of the organ, and the animal examined. Its histological 

 composition, as might have been expected, is similar to that of the 

 capsule of other related organs, consisting chiefly of white fibrous 

 tissue, with some yellow elastic fibres and involuntary muscle. Strips 

 of the capsule impregnated with silver nitrate show the arrangement 

 of the white fibres very beautifully (pi. II. fig. 14) the fibres remaining 

 unstained, while the ground substance is darkened. 



From the inner side of the capsule spring trabeculae composed 

 of the same elements as the capsule itself. These subdivide the gland 

 as above described, and vary considerably in strength and arrangement 

 in different animals. The capsule is pierced at one or more points 

 by various nerves and bloodvessels; the latter are conducted along the 

 trabeculae in the large glands; in other cases they run in strands of 

 adenoid tissue (pi. II. fig. 13). 



The lymphoid tissue is composed of a dense reticulum, in the 

 meshes of which leucocytes are enclosed; in many cases it is nodulated, 

 and rounded projections jut into the sinus. In these rounded masses, 

 which are found by an examination of serial sections to be connected 

 to the main mass of adenoid tissue, there often occur spherical patches 

 which stain less deeply than the surrounding tissue; these constitute 

 the ''Germ centres" or "Keimcentra" of the German writers (pi. I. 

 fig. 1). The cells contained in them, seem slightly swollen and shew 

 active signs of mitosis. Around the margin of the germ centre the 

 cells assume a darker stain gradually shading off into the general 

 adenoid tissue (pi. I. fig. 6). 



The presence of these centres in haemal glands was originally 

 observed by Eobertson and has since received attention from several 



