DR. H. WATNEY ON" THE MINUTE ANATOMY OF THE THYME'S. 
1089 
fig. 17). The central mass does not always completely fill the capsule (see Plate 91, 
figs. 63 and 59, a), the interval having been formed by the shrinking of the contained 
substance. The central part is sometimes found passing down the vessel-like prolonga¬ 
tions, which are attached to the concentric corpuscles (see Plate 91, fig. 59, a; and 
Plate 85, fig. 7, ce). 
The outer part of the concentric corpuscle, which we have called the capsule, is 
formed of epithelioid cells (see Plate 91, fig. 59, b; Plate 90, fig. 49; and Plate 85, 
fig. 7). These cells are flattened towards the inside of the capsule ; on the outer side 
they are polygonal, and are anatomically continuous with the branching connective- 
tissue-corpuscles, which form the network of the medulla (see Plate 86, fig. 15 ; 
Plate 91, fig. 64 ; and Plate 92, fig. 69). 
The larger concentric corpuscles, besides being connected to the network of the 
medulla, have often projections formed of epithelioid cells, very like vessels in 
appearance (see Plate 91, figs. 59, 64, and 65). Others show sharply-defined 
processes, formed of epithelioid cells, such as are shown in the lower part of fig. 17, 
Plate 86. The cells composing these processes are generally very large, and contain 
large nuclei; and the cells of the network to which they are attached are larger than 
in the other parts of the medulla. As a rule, the nearer the connective-tissue-corpuscles 
are to the concentric corpuscles, the larger they are, the coarser are their processes, 
and the larger their nuclei. Again, we often find the concentric corpuscles attached to 
one another, or to the surrounding network, by long coarse threads, which have nuclei 
embedded in them at intervals. Such are shown from teased preparations in Plate 86, 
fig. 15, th; and Plate 91, figs. 61 and 62 ; and from sections of the tissue in Plate 90, 
fig. 50, th; and Plate 92, fig. 69, th. These coarse processes often run for long 
distances across the medulla, and mark out the position of the future bands of 
connective-tissue. In other specimens the concentric corpuscles are attached to one 
another, or to fibrous trabeculae, by bundles of these coarse threads (see Plate 91, 
fig. 60) or by bands of fibrillated-tissue (see Plate 91, figs. 58 and 63). 
Having considered the structure of the concentric corpuscles, when fully formed, 
let us trace their origin. In Plate 90, figs. 50 and 49, where sections are made 
through large portions of tissue, we find the concentric corpuscles near those parts of 
the medulla where there are granular cells. We have also seen that the epithelioid 
cells, forming the capsule of the concentric corpuscles, are continuous with the epithe¬ 
lioid connective-tissue-corpuscles of the medulla (see Plate 90, fig. 49), and it is from 
these two elements, the granular cells and the epithelioid cells, that the concentric 
corpuscles are formed. As the granular cells take their origin primarily in the 
connective-tissue-corpuscles, we may say that the concentric corpuscles arise from 
connective-tissue-corpuscles ; and we shall be able to support this latter proposition in 
considering the somewhat different concentric corpuscles of the Bird and the Tortoise. 
In Plate 92, fig. 68 , is shown a medium-sized concentric corpuscle; the central part 
and the capsule are not yet differentiated from one another; and therefore we are 
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