CONCERNING SERPENTS. 



263 



diameter. This is permitted by the extraordinary expansibility of 

 their body ; but the enlargement of their jaws is a complicated phe- 

 nomenon. In the act of swallowing, they yield at every point, side- 

 ways as well as vertically. The elastic integuments which hold the 

 parts of their jaws in place give way, and the apparently small mouth 

 becomes an enormous one. 



Digestion proceeds slowly, and, if the meal be excessive, as it often 

 is, the serpent remains sluggish and comparatively helpless a long 

 time. " They have been kept four, six, and eight months, without 

 being fed, and with very little apparent waste of substance." Bruce 

 reports that he kept specimens of the cerastes, or horned-snake, two 

 years in a glass vessel without food, during which time they cast their 

 skins as usual. 



Fig. 5. 



ClKCTILATING SYSTEM OF REPTrXE. 



a. Auricle receiving worn-out venous blood from the system; a'. Auricle receiving vitalized blood 

 from the lung; v. Ventricle in which the two bloods are mixed, and from which it is thrown 

 into the general circulation. 



Vital activity in serpents is low. In mammals, the normal mean 

 temperature is from 95° to 105° Fahr., and this must be maintained, or 

 disease supervenes. With serpents, the temperature is a few degrees 

 only above that of the surrounding atmosphere, and varies with it. 

 Thus, it may range, in their healthy active state, from 60° to perhaps 

 more than 80° Fahr. The temperature of a serpent was found, by 

 Hunter and others, to be 88.46°, that of the air being 81.5°. The tem- 

 perature of a frog was 48° in water at 44.4°. If the atmosphere be 



