OF THE THYEOID GLAND OF THE DOG. 
565 
Resemblance between the contents of the Vesicles and those of the Lymphatics. — In 
conclusion I wish to draw attention to the close resemblance existing between the 
contents of the vesicles and those of the lymphatics. This resemblance will probably 
have already struck the reader from the description of these two substances given 
above (pages 560 and 562). 
There are several reasons for considering that the two substances are identical : — 
1. The general Appearance and Staining with Reagents. — In specimens prepared as 
above, and stained with picrocarminate of ammonia, they both present a granular 
appearance and stain of a yellow colour, more or less bright. In sections stained with 
haematoxylin they both present generally a uniform, sometimes a tiuely granular, aspect, 
and stain of a greyish-violet colour. 
2. The Consistence. — The reasons for considering the contents of the lymphatics to be 
during life of a viscid consistence have already been given (see above, page 562). The 
contents of the vesicles are (as stated above, page 558) described by Kolliker and Fret 
as consisting of a clear viscid fluid ; and, as far as I have seen, there appears no reason 
to doubt this assertion, though I have not directly proved its accuracy. 
From these facts it appears that the contents of the lymphatics are morphologically 
identical with those of the vesicles, and they give a strong reason for suspecting that 
the two materials are also identical in other respects. 
It is of material importance to remember that in all but one or two of the cases which 
have been examined, most of the vesicles, as well as the lymphatics, contained the 
material above described ; and it is further important to bear in mind that the material 
in the lymphatics fills and even distends the vessels completely, without containing any 
formed corpuscles ; the material cannot therefore be lymph. Hence it is reasonable 
to think that one, possibly the chief, function of the thyroid gland is the formation, within 
the vesicles, of a material which is transferred from these by the lymphatics to the 
general circulation, there to serve some purpose in the animal economy as yet unknown. 
The close relationship existing between the lymphatic tubes and the walls of the 
vesicles, together with the abundant distribution of lymphatics both within and without 
the thyroid gland, appear to lend support to this view. 
This theory is not novel; for Frey {op. cit. p. 282), speaking of the glands formed of 
closed vesicles, says: — “ The vesicles are supposed to form a secretion in their interior 
from the component parts of the blood, and to pass the same on, when ready, to the 
blood-vessels and lymphatics for removal.” He alludes to this as “ a very insufficient 
explanation.” And he may well do so, seeing that he gives no reason in support of it ; 
for neither Frey, nor any other author I have consulted, alludes to the contents of the 
lymphatics, still less to the identity (: morphological , at least) existing between the contents 
of the vesicles (where the material is supposed to Reformed) and those of the lymphatics 
(by which it is supposed to be carried off) ; nor do they give any other ground in support 
of this view. 
The thyroid gland being a body about whose function we know at present absolutely 
mdccclxxvi. 4 i 
