MR. E. C. BABER ON THE STRUCTURE OF THE THYROID GLAND. 
587 
far as examined, appears to be to the columnar form—their exact height varying in 
different animals. 
A double line of demarcation is often seen on the summits of the epithelial cells 
( e.g ., in the Tortoise). This doubtless corresponds with the cuticula described by 
Zeiss ( vide supra, p. 585) and with the appearance of a membrane lining the summits 
of the epithelial cells which I described in the Dog (op. cit., p. 5G0). 
On examining with a moderately high power (Vericik, obj. 8) a transverse section 
of the wall of the vesicles in several animals, the appearance of a fine parallel striation 
has been observed in the epithelial cells running in the long axis of the cell, and 
extending for a greater or less distance from its summit (or free extremity) towards 
the base. Examination with a higher power (such as Zeiss, obj. F) does not, how¬ 
ever, render this striation more plain, and I have not found it sufficiently distinct to 
be drawn. Thinking that this appearance was perhaps produced by intracellular 
fibrils such as Klein has described (op. cit., p. 327), I treated portions of the thyroid 
gland of the Tortoise according to the three different methods recommended by the 
author of that paper (ibid., pp. 319, 321, and 327), but without being able to see the 
.intracellular reticulum distinctly. It must be borne in mind, however, that these 
cells are much smaller than those on which Klein made his observations. 
Plate 68, fig. 8, shows an appearance probably connected with this striation. It is 
taken from the thyroid of a Kitten, injected by the method of puncture with silver, 
hardened in alcohol, and stained with hsematoxylin. In addition to endothelial mark¬ 
ings of the lymphatic, which are clearly seen (i, i), on altering the focus the epithelial 
cells are seen studded with a quantity of dots and short lines, also stained with the 
silver, which I can only explain by supposing that the ends of intracellular fibrils have 
become stained by the silver, and are seen either endways or somewhat obliquely. 
The figure which Peremeschko gives (op. cit., Plate 16, fig. 1) of a profile view of the 
processes at the base of the epithelial cells, showing minute dots arranged in parallel 
rows running in the longitudinal axis of the cells, suggests the idea that it is these 
structures which produce the appearance of dots and lines, stained with silver, just 
described, and also possibly that of the intracellular striation. My own observations 
on the existence or non-existence of processes at the base of the epithelial cells have 
not led to any definite results. 
Reticulum. —On viewing from the surface the epithelium of the vesicle in the thyroid 
gland of the Tortoise hardened in chromic acid, a delicate network is seen running 
between the individual epithelial cells, which stains darkly with hsematoxylin. (See 
Plate 68, fig. 5. In this figure the epithelial cells present in the meshes of the reti¬ 
culum are not represented.) This reticulum, which is probably formed by coagulated 
intercellular substance, is seen to be thickened at intervals. When viewed somewhat 
obliquely the meshes of the reticulum appear to be made up of delicate larnelke run¬ 
ning between the epithelial cells, although it is difficult to speak with certainty on 
this point. In spirit, and in osmic acid preparations, this reticulum is also observed 
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