DE. H. WATNEY ON" THE MINUTE ANATOMY OF THE THYMUS. 
1083 
In the early stage of development of the thymus, the blood vessels are quite small, 
and are found in the follicle and on its border (see Plate 87, fig. 23). 
The relation of the blood vessels to the granular cells, concentric corpuscles, and 
network will be spoken of in treating of those tissues. 
The Tissues composing the Coptical portion oe the Follicle. 
In thin sections of the cortex, the first feature which strikes the eye is the very 
great number of lymphoid corpuscles, which lie closely packed from the capsule to the 
edge of the medulla. They are seen to be supported by a delicate reticulum, that is, 
by a closely-meshed web, which is broadened at the nodal points. The meshes are 
very close, so that as a rule they are only large enough to enclose one lymphoid 
corpuscle (see Plate 85, fig. 9 ; and Plate 87, figs. 27 and 28). This reticulum encloses 
all the other tissues met with in the cortex, and thus resembles that which I have 
described in the mucous membrane of the intestine (see reference No. 86). 
In specimens which are stained by hsematoxylin, the difference in colour between 
the irregularly-shaped nodal points of the reticulum and the lymphoid corpuscles is 
not very great (see Plate 87, fig. 27), although the refractive powers of the two are 
very different. A great difference between the lymphoid cells and the nodal points 
is, however, noticed in specimens stained in indigo-carmine and carmine (see reference 
No. 87); for in this case the nodal points are stained of a blue-green colour, and 
the contained lymphoid corpuscles, red (see Plate 85, fig. 9). 
In sections of the cortex which have been shaken, and in which the lymphoid cells 
and the reticulum have been washed away, we have, stretching from the capsule of 
endothelial cells, a network (1) of connective-tissue threads (see Plate 87, figs. 25 
and 26, th), (2) of capillary blood vessels, and between these vessels and threads, but 
attached to both, a delicate but widely-meshed network, composed (3) of branching 
cells with long fine delicate processes (see Plate 87, fig. 25). This cell network forms 
an adventitia to the vessels (see Plate 87, figs. 25 and 26), and the connective-tissue 
threads with the network of branching cells form only one network. 
This network of cells differs in two respects from that found in any other lymphoid 
tissues of the body. In the first place, it is a permanent network of cells— i.e., it is 
not like that found in the follicles of the lymphatic gland (only a network of cells 
during very early life, to be replaced afterwards by a non-nucleated reticulum), for it 
exists as long as the thymus, and can be found in shaken specimens of the thymus of 
adult animals, as for instance, in an Ox four years old. Secondly, the network is 
unlike any other network, the cells with their very fine branching processes being 
peculiar to, and characteristic of, the cortex of the thymus gland. 
It will be seen that this network is not a reticulum of threads on which epithelioid 
cells lie, but that the processes of the connective-tissue-corpuscles, with the cell bodies, 
form the greater part of the network of the cortex. If the specimen be roughly shaken, 
