The Heart. 



55 



the animal, due to the fact that no sentient nerves are 

 supplied to the lining membrane of the bloodvessels or 

 even to the heart. It is doubtful to my mind whether 

 tracings produced by this means are completely trust- 

 worthy, for the presence of these two air-bags in the heart 

 must interfere to an extent with its normal function ; for 

 example, the experiment on p. 52 gives a pulse of sixty to 

 the minute for the horse, which is distinctly abnormal. 



A tracing obtained from the heart of the horse is shown 

 in Fio-. 1 ; each vertical line represents one-tenth of a 



Fig. 1. — Simultaneous Tracings from the Right Auricle and 

 Ventricle of the Horse, after Chauveau and Marey 

 (Foster). 

 The auricular curve is a, b, e, the ventricular curve a', &', c', d', e'. 



b, the contracting auricle which at once relaxes, and is followed by the 

 sudden upstroke in the lower curve terminating at r', indicating 

 the sharp contraction of the ventricle, which is maintained with 

 certain oscillations for about three-tenths of a second, and then 

 suddenly relaxes ; the pause follows, a part of which may be seen 

 at a and a'. 



second ; the curves do not indicate the' force of the stroke, 

 but only the intra-cardiac pressure. It is seen from the 

 diagram that the auricles contract first, followed by the 

 ventricles ; the former is slower and shorter than the ven- 

 tricular systole, which is sudden, maintained for some time, 

 and then rapidly falls. During the ventricular systole the 

 heart makes its impulse against the chest wall. 



The impulse of the heart against the chest wall is 

 obtained by means of the cardiograph, of which there are 



