MR. E. C. BABER ON THE STRUCTURE OE THE THYROID GLAND. 
593 
Plate G8, fig. 12). The opposite gland of this Dog also contained numerous vesicles 
with red blood-corpuscles. In the gland of another Dog (male, nearly 2 years old) 
numerous vesicles containing red blood-corpuscles were also present. (In these two 
Dogs the red blood-corpuscles were more disintegrated and less distinct than in many 
others, but from a study of the changes which the red blood-corpuscles undergo in the 
vesicles, I think there can be no doubt of these being of this nature.) From these 
observations it appears that in the Dog, at least, an escape of red blood-corpuscles is 
almost constantly taking place into a greater or less number of vesicles. As only a few 
sections from each gland were examined, it is obvious that the number of vesicles 
containing red blood-corpuscles in all probability greatly exceeded that actually 
observed. The frequency of the escape of red blood-corpuscles into the vesicles of 
the Dog, together with its occurrence in the glands of such different animals as the 
Tortoise and Conger Eel, I think, renders it very probable that the passage of red 
blood-corpuscles into the vesicles is a normal occurrence in the thyroid, gland. 
In the thyroid gland of a Seal ( Phocct vitulina ) which I obtained through the kind¬ 
ness of the late Professor A. H. Garrod, F.R.S., the epithelium of almost all the 
vesicles contained numerous dark red granules, which on close examination appeared to 
be minute crystals. Arguing from the appearance above-described in the epithelium 
of the Dog, I attributed these to the absorption of colouring matter from blood effused 
into the cavity of the vesicles. Subsequently also on careful examination I found that 
a large proportion, in some parts certainly the majority, of the vesicles contained 
structures which were very probably red blood-corpuscles, but, perhaps owing to the 
gland not being quite fresh, they could not be certainly identified with these. In the 
thyroid gland of the Rook, also, in one instance, yellow granules, some of considerable 
size, were seen in the epithelial wall of almost all the vesicles of both glands (see Plate 
G9, fig. 14), and yellow masses were found in the cavities of some of the vesicles which 
I was inclined to consider as fused red blood-corpuscles. A careful examination of 
these glands led me to believe that in this Bird an extensive hcemorrhage had taken 
place into the vesicles, and that the Bird was killed just as the colouring matter of the 
blood w T as being reabsorbed. 
It is possible, of course, that the glands of the Book and the Seal just mentioned, 
as well as those of the two Dogs (in which an extensive escape of red blood-corpuscles 
was observed), may be pathological in character, in which case considerable interest 
would also obviously attach to them. These observations, however, I think at least 
render it very probable that normally, under certain circumstances, an escape of red 
blood-corpuscles takes place into a large proportion of the vesicles of the thyroid gland; 
they certainly encourage to further research in this direction with a view, it possible, 
of throwing light on the function of the organ. 
The blood which thus escapes into the vesicles contributes, no doubt, to a large 
extent to the formation of the “ colloid ” material which they contain, and it seems 
highly probable that this escape of red blood-corpuscles into the vesicles, with their 
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TVIDCCCLXXXI. 
