276 Bayliss and Starling, 



the base, at the aimculo-ventriciilar groove, and spreading thence to 

 the apex. 



3. There is a considerable block at the auriculo- ventricular 

 groove to the transmission of excitation from auiicle to ventricle. 



4. The effect of using cold air in respiration, or cooling the base 

 of the ventricles by other means, is to reverse the electrical changes, 

 causing a wave of negativity which apparently starts from the apex. 



5. The effect of injuiy is similar to that observed by Sanderson 

 and Page in the frog, viz., abolition or diminution of the state of 

 excitation at the injured part. 



Appendix. 



On tlie Electromotive Changes 



connected with the cardiac Beat in Man and the Dog 



with chest unopened. 



(From experiments made in the Physiological Laboratory of the University of Oxford.) 

 To Waller is due the credit of having first discovered the possi- 

 bility of recording and studying the electromotive changes attending 

 the cardiac contraction in man and the intact animal. In his first 

 paper on the electrical change of the heart of man^), we find that he 

 observed on the electrometer two movements of the meniscus in the 

 same direction accompanying each beat, and that they were in such 

 a direction as to indicate negativity of the base to the apex occur- 

 ring twice in each beat; but no explanation is given. In a subsequent 

 paper ^) Waller gives a different account of the variation, having taken 

 photogi^aphs of the variation which seemed to show that negativity 

 of the apex ]}receded that of the base. 



In the paper to which this is an appendix, it is shewn that in 

 the dog's heart, in as normal a condition as possible when ex[)osed, 

 negativity of the base always precedes that of the apex, and the oc- 

 cuiTence of apical negativity preceding basal negativity is explained 

 as due to local cooling of the base. 



^) Journal of Physiology. Vol. VIII. p. 229. 

 «) Phil. Trans. Vol. 180. 1889. p. 169—194. 



