LYMPHATICS, ETC., OF THYROID GLAND OF THE DOG. 211 



chymatous cells originate in the intervesicular tissue external 

 to the toalls of the vesicles ; from some cause {inherent move- 

 ment or growth of cells behind them) they exert pressure on 

 the wall of an adjoining vesicle ; the cells of this become flat- 

 tened out or absorbed to a greater or less degree, and finally 

 give way, allowing the parenchymatous cells to escape into 

 the cavity, and to form a constituent of tlie contents of the 

 vesicle. 



The distribution of the parenchyma through the gland 

 appears tolerably uniform, though probably its cells are more 

 numerous between the small than between the large vesicles. 

 As above mentioned, in some places they are numerous and 

 form groups, whereas in others they appear only thinly 

 scattered on the walls of the vesicles. Having been observed 

 in all thyroid glands of the dog which were carefully examined, 

 they must be regarded as normal and constant structures. 



From the small vesicles, which they frequently resemble 

 in size, the parenchymatous cells may be distinguished by 

 the presence of the nucleus and by their being less highly 

 refractive. 



Mesemblance bettoeen the conte7its of the Vesicles and those 

 of the Lymphatics. — The description of these two substances 

 given in a previous paragraph indicates the close resemblance 

 existing between them. There are several reasons for con- 

 sidering them identical. 



1. The general Appearance and Staining with Reagents. — 

 In specimens stained with picrocarmiuate of ammonia 

 and mounted in balsam they both appear granular and of a 

 more or less bright yellow colour. In sections stained with 

 logwood they both present generally a uniform, sometimes 

 a finely granular aspect, and stain of a greyish-violet colour. 



2. The Consistence. — The reasons for considering the con- 

 tents of the lymphatics to be during life of a viscid consistence 

 have been given above under I. The contents of the 

 vesicles are described by KoUiker and Frey as consisting of 

 a clear viscid fluid ; and, as far as I have seen, there appears 

 no reason to doubt this assertion, although I have not 

 directly proved its accuracy. 



From these facts it appears that the contents of the lym- 

 phatics are morphologically identical vfiih those of the vesicles, 

 and they give a strong reason for suspecting that the two 

 materials are identical in other respecls. 



It is of material importance to remember that in all but 

 one or two cases examined, most of the vesicles, as well as 

 the lymphatics, contained the material above described ; and 



