208 E. CRESSWELL BABER. 



certain cells were observed in the latter, which, it is believed, 

 have not hitherto been described. The subjects of this paper 

 may, therefore, be treated under two headings: — 1. The 

 Lymphatics, and 2. The Parenchyma. Before considering 

 these, however, it will be necessary to say a few words with 

 regard to the general structure of the thyroid gland of the 

 dog, as observed in this research. 



First, with regard to the stro7na. In the dog, as is well 

 Icnown, the thyroid gland consists of two separate portions, 

 situate on either side of the trachea. Each of these forms, 

 apparently, a single lobe, which is divided into lobules, more 

 or less distinctly, by processes of connective tissue passing 

 inwards from the surface of the organ, where they are con- 

 tinuous with the connective-tissue capsule surrounding the 

 gland. These bands of connective tissue run chiefly with the 

 blood-vessels and gradually diminish in size till between the 

 individual vesicles it is often impossible to say that there 

 is any stroma present. On the whole the stroma appears 

 very sparing in quantity. 



The Vesicles. — Between the different ramifications of the 

 stroma are seen the vesicles with their walls, consisting of a 

 single layer of cells arranged like an epithelium, and usually 

 known as " epithelial cells." These commonly present a 

 square or wedge-shaped outline, though their shape varies in 

 different preparations and in different parts of the same spe- 

 cimen. They are usually higher than broad ; sometimes, 

 however, they present a more or less flattened appearance, 

 probably the effect of the reagents (fig. 1). Under certain 

 circumstances these cells present a more or less triangular or 

 crescentic outline, of which more hereafter. Their cell-sub- 

 stance is finely granular, and they are each provided with a 

 single spheroidal nucleus. With regard to the existence or 

 not of a mcmhrana propria outside the epithelial cells I am 

 not in a position to make any definite statement. 



Contents of the Vesicles. — The contents of the vesicles 

 consist, in addition to a small quantity of a pellucid sub- 

 stance sometimes present, of a jieculiar material, which 

 shrinks avvay from the walls of the vesicle and forms a solid 

 mass in the centre (fig. 1, c). In sections stained with picro- 

 carminate of ammonia it appears as a finely granular sub- 

 stance, of a more or less bright yellow hue, contrasting with 

 the red colour of the walls of the vesicles. 



In specimens coloured with hsematoxylin, on the other 

 hand, it presents the aspect of an opaque, grey, or greyish- 

 violet mass, which is generally uniform, but sometimes 

 finely granular in appearance. 



