596 
MR. E. C. BABER ON THE STRUCTURE OF THE THYROID GLAND. 
Pigment .—Masses of brown pigment-granules were frequently seen in the homo¬ 
geneous material in the thyroid glands of the Frog. They are probably the result of 
an escape of red blood-corpuscles into the vesicles, but this point could not be ascer¬ 
tained for certain. Numerous brown pigment granules were also sometimes seen in 
the homogeneous material in the vesicles of the Conger Eel. 
IV. Parenchyma. 
In my previous paper on this subject (op. cit., p. 563) I described and figured, as 
normal structures in the thyroid gland of the Dog, some large round cells provided 
with a single oval-shaped nucleus, to which I applied the term “parenchymatous cells.’ 
From the different appearances they present and their different positions in regard to 
the wall of the vesicle, I concluded that a migration of these cells takes place into the 
cavity of the vesicles by displacement and compression of the epithelial cells. 
Zeiss (the only observer, as far as I am aware, who has since written on the sub¬ 
ject) has been unable to observe any such migration of cells into the vesicles. In 
order to see these cells well, it is of course necessary that the sections should be 
very thin. 
To the description of these cells in the Dog, as given in the above paper, I have little 
to add. I have since also observed them in the glands of young Dogs (aged 5 and 
9 weeks respectively). Whilst still maintaining the view that these cells migrate 
into the cavity of the vesicles, I think it is quite possible that some of them may 
originate between the epithelium of a vesicle and the capillaries, and from thence pass 
by compression or separation of the epithelial cells into the vesicle. 
In the thyroid gland of the Cat, parenchymatous cells are also present in consider¬ 
able numbers, although not nearly so numerous as in the Dog. They resemble very 
much those seen in the latter animal, and appear to migrate into the vesicles in a 
similar manner. A few cells, apparently of similar character, have also been seen in 
the thyroid of the Pabbit. 
In the thyroid of the Pigeon large groups are frequently seen, consisting of cells, 
which are larger than the adjacent epithelial cells (see Plate 69, fig. 15). They are 
round or oval in shape, and are provided each with a single spherical or oval-shaped 
nucleus. They resemble very much the parenchymatous cells seen in the Dog; but 
whether they, like them, migrate into the vesicles I am unable to say, as I have not 
observed any of them in the substance of the epithelial walls. 
Pound cells were sometimes seen in the epithelium of the Skate, but the nature of 
these could not be ascertained. In the Conger Eel groups of cells somewhat rounded 
in form were found amongst the cylindrical epithelial cells, but in all probability these 
were connected with the origin of the small vesicles in the walls of larger ones, as 
above described. 
