THYREOID IN TURTLES 287 



turn join to form larger trunks (the interlobular canals). These 

 last follow the course of the arteries, veins, and nerves till they 

 reach the external surface of the gland, where they form a dense 

 network, from which emerge the larger branches through which 

 the lymph is emptied into the lymphatic gangUa of the neck. 



The innervation of the thyreoid is by the sympathetic. The 

 fine non-meduUated fibers accompany the arterial ramifica- 

 tions in the gland. The vagus also sends two fine branchlets 

 into the gland through the laryngeal nerves, but their distribu- 

 tion is not constant. 



HISTOLOGY 



For the microscopic study of the thyroid of Emys europaea I 

 have made use of specimens preserved in — 



1. Formalin, from 5 per cent to 10 per cent aqueous solution. 



2. Mercuric chloride 



3. Zenker's fluid 



4. Flemming's fluid 



5. 96 per cent alcohol 



6. Miiller's fluid 



The sections were stained in different ways. For the general 

 study of the thyreoid tissue, preservation in 10 per cent formalin 

 and staining with Ehrlich's acid-haematoxylin and the aqueous 

 solution of eosin gave good results. Fixation in Flemming and 

 staining with ferric haematoxylin (Heidenhain) and eosin per- 

 mitted greater accuracy in studying the delicate structure of the 

 cellular elements. Safranin and carmine have been very useful 

 in dehcate cytological study. For studying the elastic fibers 

 fucselin and Weigert's fluid were used combined as follows: 



a. Fucselin. 



b. Fucselin- Van Gieson: Weigert's fluid. 



c. Weigert's fluid; borax carmine, alcoholic solution of the 

 Naples Zoological Station. , 



d. Weigert's fluid safranin. 



e. Safranin, picric acid, Weigert's fluid. 



There is no substantial difference in structure between the 

 thyreoid of Emys europaea and Testudo graeca and that of the 



