322 THE LARYNX, LUNGS, VOCAL SACS, ETC. 



general appearance is seen in Fig. 211 III ; tliey show a concentric 

 striation and usually enclose one or more smaller cells. They 

 therefore closely resemble similar corpuscles found in higher 

 animals. 



(y) In many frogs the cellular structure of at least a part of 

 the gland seems to have undergone a degenerative stage (III). In 

 such cases the connective-tissue is increased in quantity, and marks 

 off portions of the section into small lobules (III) which are 

 filled with cells containing mucus or sometimes fat (III). Under 

 what conditions this degeneration, if such it be, takes place has 

 not yet been determined ^. 



(Ô) Large branched pigment-cells are found in the course of the 

 larger blood-vessels. 



(e) Watney describes also four varieties of ' granular cells : ' 

 I. polygonal or rounded; 3. vacuolated; 3. spheroidal masses; 

 4. club-shaped masses attached to the blood-vessels. I have, how- 

 ever, not been able to distinguish them. J 



[Tolldt {I.e. 1S68) described the lymphoid tissue and the blood-vessels of this gland 

 but did not find the corpuscles of Hassall. 



Fleischl (I.e. 1870) disputed Tolldt's descrijDtion ; he evidently found the corpuscles 

 of Hassall (see Fig. 211 IV), but he held them to be nerve-cells, and described them 

 as such. He was also of opinion that the blood-vessels open into the intercellular 

 spaces (as in the spleen). This has not been found to be the case by any other 

 observer. Watney (I. c. 1882) first described the concentric corpuscles of Hassall 

 as such. 



Most writers describe the parenchyma as arranged in lobules. This I have only 

 seen in a part of the gland and under what I believe to be pathological conditions.] 



V. THE THYEOID GLAND. 



a. General description. A thyroid gland (Fig. 209 Thy) is 

 found on either side as a small, triangular, or oval, reddish-coloured 

 body on the dorsal surface of the M. sternohyo'uleus, just before 

 it passes between the MM. genio-hyoide.i. It lies in the angle 

 formed between the larger and smaller posterior eornua of the 

 hyoid {IIH, HH^). It is easily found by the presence of a large 

 number of vessels in its neighbourhood, and especially by the 

 large jugular vein, to the ventral surface of which it is intimately 

 attached. 



' Only winter-frogs were at my disposal (translator . 



