258 THE DUCTLESS GLANDS 



generally. The gland is distinctly more vascular than in the 

 frog. 



In Triton there appear to be two, or even three, parathyroids 

 developed on either side. In Sperlerpes there is sometimes 

 only one. The general histological features appear somewhat 

 different from those of the corresponding structure in the frog. 

 The body is of extremely small dimensions, but contains fairly 

 large blood capillaries. It is encapsuled, but its constituent 

 cells do not possess the whorl arrangement so characteristic 

 of7the parathyroids of the frog. 



The post-branchial body occupies a corresponding position 

 to that in the frog ; it consists of about eight vesicles. These 

 have a taller epithelium than the thyroid vesicles and contain 

 colloid. 



5. In the Anura (a) the thyroid has been most carefully 

 studied in the frog. In this animal the gland of each side is 

 an oval corpuscle placed ventrally to the root of the processus 

 postero-medialis of the hyoid cartilage, and occupies a deep 

 concealed position. It is very difficult, as a rule, to find by 

 ordinary dissection. 



Like the thyroid of all animals, that of the frog consists 

 of a number of closed vesicles, the walls of which are composed 

 of a single layer of epithelial cells. The cells lining the vesicles 

 are cubical, but small, corresponding with the small size of the 

 vesicle and of the whole gland. The intervesicular tissue, 

 instead of being cellular as in mammals, is formed of fibrous 

 connective tissue with scattered nuclei and bloodvessels. The 

 colloid contents of the vesicles call for no special notice. 



(b) Accessory thyroids are not uncommon in the frog ; 

 they have the same structure as the main thyroid. 



(c) Parathyroids in the frog are first mentioned by Ecker, 

 who considered them as representatives of the thymus, and 

 by Leydig, who considered them, together with the " ventral 

 branchial body," as representing the thyroid. That they are 

 very different from the thyroid in their structure Leydig 

 himself stated. The suggestion that one of the bodies de- 

 scribed by Leydig was the ventral branchial body and the 

 other the parathyroid is made by Gaupp, and on referring to 

 Leydig's monograph and looking at his plates, it seems clear 

 that this is the case. After the work of Toldt, the bodies were 

 called for some years " Nebenschilddrusen," a term which 



