or THE THYROID GLAND OP THE DOG. 
563 
In sections stained with hsematoxylin the contents of the lymphatics usually present 
a uniform appearance, but are sometimes finely granular. They stain of a faint greyish- 
violet colour. 
In addition to this peculiar material, a few globules of a hyaline substance sometimes 
appear in the lymphatics. 
II. Parenchyma. 
Besides the stroma, lymphatics, blood-vessels, &c. between the vesicles, there is 
another tissue, to which, as far as I am aware, no allusion is made by authors on this 
subject. 
To this tissue I propose to give the name of “ parenchyma,” on the supposition that 
it is possibly analogous to the parenchyma of the testis as described by Kolliker, Henle, 
and Michalkovitch. 
Characters of the Parenchyma. — On examining with a high power (as Verick’s obj. 8) 
specimens stained with hsematoxylin and mounted in balsam, the attention is attracted 
by numerous cells differing markedly in size and shape from the epithelial cells amongst 
which they lie. 
These cells present usually a more or less rounded appearance, and are considerably 
larger than the adjacent epithelial cells. Their cell-substance is finely granular, and they 
are each provided with a single large nucleus. 
It frequently happens that these cells present an irregular outline, being at the same 
time smaller, as if the cell-substance had shrunk up round the nucleus. When this is 
the case a space is left between it and the surrounding structures ( vide figs. 8, b, 10, b , 
11, b, 12, b, 14, b, and 15, b). At some parts of the specimens, however, this is not the 
case, and the cell-substance then presents a regular rounded outline, and is in contact 
with the neighbouring elements (vide figs. 9, c & 12, c). 
The nuclei of the parenchymatous cells are round or oval in shape, and have a well- 
marked outline. They are larger than those of the epithelial cells, and do not stain 
quite so darkly with hsematoxylin. In their interior are seen several nucleoli. 
The parenchymatous cells are met with either alone (figs. 8 & 13) or in groups (figs. 
9, 10, 11, 12, 14, & 15). In the latter case several (often three) frequently appear to be 
situate in a common cavity, which they do not fill out, as shown in figs. 10, 11, & 14. 
As regards the position occupied by these cells, and their relation to the walls of the 
vesicles, four different appearances at least are presented : — 
1. The cells are situate, either singly or in groups, external to the vesicles, and sepa- 
rated from their cavity by a layer of normal epithelial cells (i. e. epithelial cells as 
described above at page 560). See figs. 10 & 15. 
2. Other parenchymatous cells, also situate in the intervesicular spaces, are seen to be 
separated from the cavity of the adjoining vesicle by a layer of flattened epithelial cells , 
the latter presenting a concave surface to the parenchymatous cells. See figs. 8, 
9, & 11. 
3. Some parenchymatous cells are seen encroaching on the layer of epithelial cells to 
