MR. E. C. BABER ON THE STRUCTURE OF THE THYROID GLAND. 
585 
In this connection it may be well to mention the following appearance which I have 
observed in the thyroid gland of several Conger Eels :—In the walls of the vesicles, 
which in this animal are often of considerable size in proportion to the whole organ, 
small vesicles are seen, as shown in Plate 68, fig. 4. These secondary vesicles (Plate 68, 
fig. 4, 3, 3 ) are provided with an epithelial wall, and with contents similar to the 
primary vesicles. From the fact that by their growth they have evidently flattened 
out to a greater or less degree the epithelium separating them from the cavity of the 
primary vesicle, it is probable that the two layers of epithelium separating the cavity 
of the small, from that of the large vesicle sometimes give way, allowing the contents 
of the two vesicles to mix. At the same time others of these small vesicles probably 
grow outwards becoming independent structures (Plate 68, fig. 4, 5 , 5 ). It is possible 
that some of these small vesicles may be curved branches of a large one which are cut 
across in the section. 
II. Epithelium, Reticulum, and Basement Membrane. 
The wall of the vesicle is composed of a layer of epithelial cells, and also, according 
to some observers, of a basement membrane and reticulum. 
Results of previous observations. 
Epithelium .—Pecent observers are not yet in accord in regard to the shape of the 
epithelial cells. Verson ( loc. cit.) describes the epithelial cells as higher than broach 
Boechat, on the contrary (op. cit., p. 20), considers that in the normal state their 
breadth exceeds their height. Peremeschko (op. cit., p. 281) is of opinion that in all 
animals, without exception, they are cylindrical, “ but where the vesicles are enlarged, 
as in old animals, the epithelial cells present the most bizarre forms, which without 
doubt results from the mechanical pressure.” Zeiss (op. cit., p. 20) finds their shape 
in the Sheep and Calf highly cylindrical; in Man and in the Pat, shortly cylindrical; 
in the Cat, Dog, and Rabbit, cubical. He insists that the normal shape of these cells 
is not flattened but cylindrical. He also states that he has never found cubical and 
cylindrical cells in immediate proximity, but has not uncommonly seen vesicles with 
cylindrical cells next to those containing a cubical epithelium. Processes attached 
to the base of the epithelial cell have been observed by Peremeschko and Zeiss. 
Peremeschko noticed that the surface of the cell turned towards the cavity of the 
vesicle (summit of the cell) has a bright margin. Zeiss confirms this observation (on 
fresh cells examined in saline solution), and describes the bright margin as a cuticula. 
Reticulum.— Z eiss (op. cit., p. 23 ) has observed between the epithelial cells a fine 
reticulum, similar to that described by Von Ebner and Schwalbe in other glands 
provided with a cylindrical epithelium. He describes it as a network of delicate rods 
on the two surfaces of the epithelium with fine processes, or lamellae, extending 
between the epithelial cells. In osmic and chromic acid preparations it presents 
MDCCCLXXXT. 4 G 
