VASCULAR GLANDS THYMUS GLAND. 



225 



substance, that divide it into "acini" or gland-granules. Isolated gland- 

 granules of the same kind are frequently to be met with on the main canal 

 (Fig. 96, c). The parenchyma of each lobule or follicle is made up of a 

 plexus of connective-tissue fibres with interspaces which contain lymph- 

 corpuscles ; larger coarsely granular spheroidal bodies composed of proto- 

 plasm, and containing one or several nuclei j 1 and Hassall's concentric cor- 

 puscles, which, as Ecker has pointed out, may be either simple or compound. 

 The former are spheroidal vesicles with a concentrically striated investment, 

 and either contain a homogeneous substance exhibiting fatty lustre, or con- 

 tain granular material and a nucleus in their interior. The latter are much 

 larger bodies, and consist of several simple vesicles inclosed by a concentri- 

 cally striated common investment. Both forms become more numerous as 

 the gland advances to complete maturity. The vessels, which are numerous, 

 especially during the period of the functional activity of the organ, pene- 

 trate the follicles at many points of their surface, and anastomosing fre- 

 quently form a close plexus in the interior (Fig. 98). Between the vessels 

 and attached to them as well as to the connective tissue of the septa, an 

 exceedingly compact but very delicate network is extended, chiefly formed 



Fir,. OS. 



FIG. 99. 



4000 in 



FIG. 98. Transverse section through an injected lotmle of the Thymus in a child: a, membranous 

 investment of the lobule ; b, membrane of the gland-granules ; e, cavity of the lobule, from which the 

 larger vessels branch out. 



FIG. 99. Thymus-juice rich in corpuscles, with a few secondary molecules, and the structureless 

 minutely granular base. 



by the anastomosing branches of multipolar cells, in the interstices of which 

 are numerous lymph-corpuscles; in addition a narrow-meshed network may 

 be observed, which is formed by the prolongations of the interfollicular 

 lymphatic vessels. The whole structure of the follicles resembles that of 

 the Peyerian bodies. 



163. The lymphatics of the interior of the follicles open into cavities lined 

 by endothelium surrounding the follicles, which again communicate with 



Anttt., \ 208; Mr. Simon's Physiological Essay 

 o, Zeits f. wis* Z<>ol., Bd. xxviii, p. 147; Mr. 



i See Prof. Kollikor's Mikro^cop 



on the Thymus Gland; Ppromfsph . 



Gulliver's Lecture, iv. Mod. Time-* and GMZ., 1863. vol. ii, p. 503; and Klein in 

 Strieker's Manual of Histology (Syd. Soc. Transl. 1 ), vol. i, p. 365. 



