586 
MR. E. C. BABER ON THE STRUCTURE OF THE THYROID GLAND. 
branched stellate figures, occasionally provided with nuclei having an indistinct 
contour. The reticulum extends on both aspects slightly beyond the level of the epi¬ 
thelium. He also describes in a profile view narrow rod-like structures between the 
cubical or columnar epithelial cells, resembling the club-shaped cells (“ Keulenzellen ”) 
described by Schwalbe in Brunner’s glands of the Dog. 
Basement membrane .— Kolliker, Henle, and Verson have described a very fine 
homogeneous membrane (membrana 'propria .) lying outside the epithelial cells. 
W. Muller also found a thin membrana propria in the vesicles of Man, Fowl, and 
Pig. Frey has been unable to see this membrane. Peremeschko (op. cit., p. 281), 
although he denies having seen a membrana propria, concludes that the cavities of the 
vesicles are formed by the epithelial cells, which are situated directly on the sur¬ 
rounding connective tissue, which forms a homogeneous, membranous limiting laver 
(“ Grenzschicht”). Boechat also denies its existence, and considers that the epithelial 
cells are in direct contact with the endothelium of the lymphatics at a great number 
of points. The two walls (the endothelium and epithelium) are, he considers, sepa¬ 
rated at certain points by the bands of connective tissue which form the framework of 
the gland, and by capillary blood-vessels which ramify between them (p. 39). Zeiss 
(op. cit., p. 15) has not been able to find any membrana propria of the above descrip¬ 
tion, nor any structure resembling the “ Driisenkorbe” of Boll. He has always 
observed between the endothelium of the lymphatics and the epithelium of the 
vesicles a very fine layer of connective tissue, in which he thinks that the capillaries 
ramify (p. 44). 
Observations. 
Epithelium .—The discrepancy of opinion of different observers in regard to the 
shape of the epithelial cells is, I think, attributable to three chief causes :— 
1. The varying shape of these cells in different animals. 
2. The different re-agents employed in examining and hardening the organ. 
3. The state of functional activity of the gland at the time of removal. 
With regard to re-agents I have chiefly examined these cells in specimens hardened 
in the usual way in alcohol—others, however, have been examined after being hardened 
with other re-agents, or in the fresh state. When it is found, however, that in the 
glands of the same species of animal prepared by a similar method, the appearance of 
the epithelial cells differs considerably, one is forced, I think, to admit the third factor 
above mentioned. Making due allowance for the two last-named elements of uncer¬ 
tainty, I have found that the general character of these cells in different animals is as 
follows:— 
In the Dog, Cat, Kitten, Babbit, Sheep, Book, Pigeon, and Frog the epithelial cells 
are cubical or slightly columnar. In the Seal and Tortoise they are distinctly 
columnar. In the Horse, Skate, and Conger Eel they are highly columnar in shape. 
The general tendency, therefore, of these cells throughout the vertebrate series, as 
