332 Canadian Record of Science. 



responding one in the Terrapin ; but, generally, the increase, 

 in force of the cardiac beat has been greater than the increase 

 in rate. 



3. Stimulation of the ganglion cardiacum basale, or the 

 main stem beyond it, to the next metamere below, gives 

 decided accelerating effects. 



I have thought that stimulation of branches from this 

 ganglion connected with the brachial plexus had acceler- 

 ating effects, but of this I do not feel quite certain. The 

 same laws as have been laid down for vagus acceleration 

 apply in this case, especially the law of inverse proportion. 



IX. Further comparison of the Chelonians. 



By way of comparison, I have made a series of experi- 

 ments on a limited number of specimens of one genus of 

 land tortoise {Pyxis). 



In most respects, the heart of this tortoise behaves more 

 like that of the Terrapin than of the sea-turtle. The heart's 

 general appearance is also more like that of the former. In 

 the sea-turtles, some species have the ligament at the apex 

 of the heart very highly developed, fibrous bands extending 

 often halfway up the ventral surface of the ventricle ; and 

 with great breadth of apical attachment. The ventricle is 

 also, in the sea-turtles, paler, of less vitality and much more 

 sensitive, as before pointed out, than in the other Chelonians. 



In the specimens of the land tortoise examined by me. the 

 holding power of the left vagus has been less than the right, 

 and I think such differences are better marked than in the 

 water tortoises or marine turtles. 



The superiority of the right auricle has been better shown 

 in the marine turtles than in the other Chelonians I have 

 studied. 



The independent rhythmic tendencies are greater in the 

 land tortoise, I am inclined to believe, than in most other 

 Chelonians. 



The land tortoise and Terrapin resemble each other more 

 than they do the marine turtles in the amount of dilation 

 following direct faradisation of the heart; also neither the 

 Terrapin's nor the land tortoise's heart enter with the same 

 facility into intervermiform action as the sea turtle's. 



