THE THYROID GLAND. 



323 



Fig. 212. 



7 



Not uncommonly several smaller supplemental glands are found 

 in the rich anastomosis surrounding the organ. 



The dorsal surface of the 

 gland is tabulated, the ventral 

 sin-face flatter and convex. 

 The glands of opposite sides 

 are seldom symmetrical. 



b. Minute structure (Fig. 

 212 I and II). [The gland 

 possesses a connective-tissue 

 capsule, which sends in trabe- 

 culae to support the vesicles of 

 which the gland is composed. 



The vesicles (I and II), 

 which vary greatly in size, are 

 closed cavities, usually of a 

 rounded or oval form, but some- 

 times branched (Baber). Each 

 vesicle is lined with a single 

 layer of cubical or slightly 

 columnar epithelium (II, a), 

 which rests on a delicate 

 basement-membrane of con- 

 nective-tissue, placed between 

 the epithelium and the sur- 

 rounding lymphatics (Baber). 



Zeiss describes a delicate reti- 

 culum between the epithelial 

 cells. 



The vesicles always contain 

 mucus (), and are surrounded 

 by a fine anastomosis of blood- 

 vessels (<?).] 



Minute structure of the thyroid gland of Rana 



esculenta. G. H. 

 I. Section through the gland (Hartnack, Oc. I, 



Syst. 3). 

 II. Small portion of above (Hartnack, Oo. I, 



' 7>- 



a Epithelium lining the vesicles. 

 6 Mucus, 

 c Blood-vessels, injected with blue mass. 



VI. THE LYMPHATIC GLANDS OF THE HYOID 

 REGION (TONSILS?). 



a. [General description. These are two oval, reddish-coloured, 

 soft lymphatic glands, placed one on each side of the larynx. 

 Frequently they are divided into two or three lobes by more or less 



Y 2 



