MR. E. C. BABER ON THE STRUCTURE OF THE THYROID GLAND. 
591 
the present research. In the youngest Dog examined (5 weeks old) the vesicles were 
almost filled with a granular material, with smooth outline, which assumed a grey 
tint on staining with haematoxylin. In the remaining Dogs the quantity present 
varied very much. At one time the vesicles appeared completely filled with it, 
whereas at another time it formed a shrunken mass only occupying a small portion 
of the cavity. The intensity with which this material took the haematoxylin or picro- 
carminate stain also varied much in different glands. It may be conjectured that 
this variation in the amount present corresponded to different states of functional 
activity of the gland. 
A substance apparently similar was found in greater or less quantity in the thyroids 
of all the other Mammals examined. It varied however greatly in amount. 
Birds .—A similar substance was observed in the thyroid glands of the Fowl and 
Pigeon. The thyroid glands of two Rooks were examined ; in one of these Birds the 
vesicles in both glands were found almost filled with a homogeneous material staining 
more or less with haematoxylin. In the second Rook, on the other hand, a very few 
vesicles contained this material, the great majority of them appearing either empty 
or much compressed. 
In the thyroids of all the Tortoises examined (14) the vesicles were found almost or 
entirely filled with this homogeneous material. 
In the Frog an apparently similar homogeneous material was invariably present. 
Its outline was usually much indented. 
Fishes .—In the Conger Eel the vesicles contained a homogeneous material, often 
with indented edges. In haematoxylin specimens sometimes, whilst this material 
presented a yellow colour, its central portion, to a greater or less extent, was of a 
bright violet tint. Rounded masses staining more or less with haematoxylin were 
often found in the vesicles. 
In the Skate in one instance the vesicles contained a comparatively small quantity 
of homogeneous material, which was much shrunk and contained numerous clear 
round spaces. In other glands the contents of the vesicles consisted of coarsely 
granular masses or of globules of various sizes. 
From the description just given there can be no doubt, I think, that, in adult 
animals at least, the homogeneous or granular material corresponds with the “ colloid 
substance” of authors, and from its almost universal occurrence in the gland-vesicles 
of adult animals, I have no hesitation in regarding it as a normal product of the 
organ. 
When this homogeneous material shrinks away from the walls of the vesicle its 
outline often presents an indented appearance, as if beset with pellucid drops (see 
Plate 68, figs. 10 and 11, taken from the Tortoise, and Plate 68, fig. 4, from the 
Conger Eel). These have been considered as drops of colloid adhering to the walls 
of the vesicle (see above— Peremeschko), For my own part I regard this appearance 
merely as the result of contraction of the viscid material (colloid) contained in the 
