CH. XXL] 



THE ELECTRO-CARDIOGRAM 



245 



chambers, and that the left and right sides are contracting 

 simultaneously. One would therefore anticipate that there would 

 be a corresponding complexity in the electrical record of the intact 

 organ. This expectation has been verified by later work in which 

 investigators have used more sensitive instruments. But there was 

 some indication of this even in the records of the earlier workers 

 who employed the capillary electrometer. Thus Bayliss and 

 Starling described in the mammalian heart a triphasic variation, 

 and Gotch by means of careful experiments on both cold and warm 

 blooded animals, has shown that this is explicable in the following 



FIG. 226. Human heart. Electro-cardiogram, EE, and simultaneous cardiogram, CC. Time, tt, is 

 marked in ^th second. The lead-offs to the capillary electrometer were from the mouth to the 

 sulphuric acid, and from the left foot to the mercury. (Waller.) 



way. Leaving out of account complications due to auricular 

 activity, he has shown that the contraction process in each ventricle 

 and its electrical concomitant commences at the part of the base of 

 the ventricle where it is continuous with its respective auricle ; the 

 contraction wave travels to the apex and returns to the part of the 

 base from which the aorta on one side and the pulmonary artery on 

 the other side arise. An electrode placed on the base will therefore 

 record the increased positivity at the beginning and the end of the 

 ventricular contraction; the electrode on the apex will record the 

 middle phase when the contraction wave reaches that point, and 

 causes an increase of positivity there. 



By far the most delicate instrument now in use is Einthoven's 

 String Galvanometer (see p. 121), and during the last few years it 

 has been much employed, not only by Einthoven himself, but by 

 numerous other observers, including Dr T. Lewis, in this country. 

 The excursions of the thread or string can be photographed, and the 

 following diagram is a cardio-electrogram obtained from the human 

 heart during a single beat, the electrodes being connected with the 

 right and left hands. 



It will be seen that there is a small movement due to the 

 auricular systole, and several large ones which accompany ventricular 

 contraction. The exact meaning of these different waves is still far 



