302 COHN— MECHANISM OF THE HEART BEAT. [April 23, 



are influenced at the same time when they are stimulated. We have 

 indeed shown that this is the case. But our main concern has been 

 to obtain information about essential differences; the likenesses and 

 the additional influences exerted will be apparent. In this problem 

 again, the galvanometer has been invaluable. On the basis of ordi- 

 nary mechanical records, of which we have made many in the course 

 of this work, we could not have drawn the conclusions just detailed. 



Stimulation of the augmentor nerves shows that these have dis- 

 tributions similar to those of the inhibitors. Rothberger and Winter- 

 berg have contributed these facts. They have shown that stimulation 

 of one or other augmentor nerve produces efifects which can be re- 

 ferred to a modification of the function of the special cardiac tissues 

 we have discussed in connection with the inhibitory nerves ; and they 

 have also shown that other differences of an electrocardiographic 

 nature take place. 



We have traced, in recording the newer aspects and methods of 

 the study of the heart-beat, the influence exerted by the introduction 

 of electrical methods. Advances by this method were due in large 

 measure to the construction of an adequate galvanometer. But the 

 advances in our understanding of the tieart have depended on detailed 

 anatomical and physiological investigation of the newly discovered 

 structures in the heart itself. How small a portion it is that has 

 been studied in relation to the whole heart, and how relatively few 

 functions of the efficient organ have been included in the recent in- 

 vestigations, has been indicated. Much remains to be done by the 

 means at our command, but much also by others still to be devised. 



Hospital of The Rockefeller Institute 

 FOR Medical Research, New York. 



