[THOMPSON] CERVICAL REGION OF THE FROG 69 
THYMUS. 
The general anatomy and structure of the thymus in the frog is 
well known. The histology is very complieated and very difficult to 
understand. It is constituted of a great variety of structures, concerning 
the meaning of which there is much controversy. 
It has been pointed out by other observers’ that the gland 
undergoes diminution of function during the period of hibernation. 
This has taken place to such a degree in the frogs obtainable here, R. 
pipiens and other species, that I have never been able to discover the 
body during the winter months. It would appear however, that the 
degree of this winter shrinkage of the thymus varies in different species 
and in different localities. In Edinburgh the body was readily found in 
the winter and extirpation experiments carried on.” 
Here in Manitoba where winter is longer, possibly the diminution 
in volume is greater. 
The description of the histological structure must be held over for 
a future communication. 
I desire to express my thanks to Professor Swale Vincent for the 
use of his laboratory and his assistance during the work. 

! Ver Ecke, Bull. de l’akad. roy. de med. de Belge. 
? Swale Vincent, Proc. Physiol. Soc., July 25, 1903, in Journ. of Physiol., Vol. 
30, 1904, p. 16. 
