590 
MB. E. C. BABER OR THE STRUCTURE OF THE THYROID GLAND. 
Under the microscope the colloid substance is either quite amorphous and homo¬ 
geneous, or amorphous and slightly granular (Virchow), or it encloses cells, or debris 
of cells, and granules (Virchow, Kolliker). 
Boechat describes the appearance it presents when coagulated by re-agents, 
namely, that of bard masses of rounded shape with regular or jagged borders. 
Zeiss observed true colloid masses in the smaller follicles, appearing in specimens 
prepared in Muller’s fluid as homogeneous, round, bean or egg-shaped masses, which 
are rarely granular, with a peculiar bluish or yellow tint, and often consisting of 
concentric layers. He found that these are at first suspended in the clear fluid, but 
soon accumulate layer upon layer on their surface, until they completely fill the 
vesicle. 
The colloid substance is considered by Henle and Kolliker as pathological in 
character, whilst Boechat and Peremeschko regard it as a physiological product. 
Zeiss, although agreeing with the last-named observer in having found it present in 
all Mammals examined, expresses no opinion either way. Ley dig has also found it 
present in bony Fishes, Sharks and Bays, in Beptiles and Birds, and on that account 
he is not inclined to regard it as a pathological product when occurring in man. 
Observations. 
The following are the chief constituents of the contents of the vesicles which have 
been observed. They are considered entirely from a morphological -point of view, 
and are described as they appear in specimens which have been hardened in alcohol, 
unless the contrary is stated. (Some of the specimens had been previously injected 
with Berlin blue or with nitrate of silver.) 
(a) Homogeneous or granular material (“ Colloid ”). 
(b) Red blood-corpuscles. 
( c ) Colourless blood-corpuscles. 
(d) Rounded masses, which stain darkly with hsematoxylin or of a bright 
yellow colour with picrocarminate of ammonia. 
(<?) Crystals and Pigment. 
(a) Homogeneous or granular material. — Dog. —It will be convenient to describe 
first more fully the appearance of this substance in the Hog, and afterwards to 
mention its characters in other animals. In my previous paper (op. cit ., p. 560) I 
described in the vesicles of the Hog’s thyroid gland a peculiar material, which in 
hardened specimens shrinks away from the walls of the vesicle and forms a solid 
mass in the centre. In sections stained in picrocarminate of ammonia it appears as a 
finely granular substance, and stains of a more or less bright yellow hue. In specimens 
coloured with lnematoxylin, on the other hand, it presents the appearance of an opaque, 
grey, or greyish-violet mass which is generally uniform, but sometimes finely granular 
in appearance. This substance v r as present in all the Hogs (10 animals) examined in 
