Electromotive Phennm. of the Mammal. Heart. 261 



alteration in our results, from a variable apex-base or base-apex-base 

 curve to a constant dipliasic variation of the nature of a base-apex 

 curve. Remembering then the effect of local cooling- on the duration 

 of the negative phase at the cooled point, described by Sanderson and 

 Page, we thought it possible that the change mighi l)e due to the em- 

 ployment of warmed air, and in fact, this turned out to be the case. 



The following experiment illustrates the sensitiveness of the elec- 

 trical variation to changes in the temperature of the respired air. 



Jime 17th. Dog. Operation as already described. Artificial re- 

 spiration with ivarmed air. 



Base of right ventricle to acid. 



Apex of left ventricle to mercury in capillary. 



Character of curves: — 



a) Before opening pericardium. 

 Diphasic. Base — Apex. 



b) After opening pericardium. 



Diphasic. Base — Apex. (Fig. 4. Plate XV.) 

 The hot water was now poured out of the vessel surrounding the 

 spillai tube and replaced by ice; after 5 minutes another photograph 

 was taken and found to be triphasic. 



c) Triphasic. Base — Apex — Base. (Fig. 5.) 

 After another five minutes: 



d) Diphasic. Apex — Base. (Fig. 6.) 



The ice was now removed and hot water replaced. After 10 minutes 

 the variation was once more diphasic, the base becoming negative first. 



e) Diphasic. Base — Apex. (Fig. 7.) 



Cold air was then used again, with the same result as before. 



We found that it was possible to imitate these results in a 

 simple way by placing a lump of ice in close proximity to the base 

 or apex of the ventricle respectively. Cooling the hase by this means 

 was found to have the same effect as the use of cold air in respiration. 



When cooled air had been made to produce a variation indicating 

 apex negativity preceding base negativity, it was found that the nor- 

 mal variation (base negativity preceding apex negativity) could be 

 reproduced by cooling the apex with a lump of ice. 



