SUCCESSION OF THE MOVEMENTS OF THE HEART. 



45 



ternal intercostal muscle over the point where the apex-beat is felt. A little bag, stretched 

 over two metallic buttons separated by a central rod, is then carefully secured in the 

 cavity thus formed, and connected by an elastic tube with the registering apparatus. 

 All the tubes are provided with stop-cocks, so that each initial bag may be made to com- 

 municate with its lever at will. When the operation is concluded and the sound firmly 

 secured in place by a ligature around the vein, the animal experiences no inconvenience, 

 is able to walk about, eat, etc., and there is every evidence that the circulation is not in- 

 terfered with. The cylinders which carry the paper destined to receive the traces are 

 arranged to move by clock-work at a given rate. The paper may also be ruled in lines, 

 the distances between which represent certain fractions of a second. Fig. 19 represents 

 the apparatus reduced to one-sixth of its actual size. Two of the levers are connected 



FIG. 19. Cardiograph. (Chauveau and Marey.) 



The instrument is composed of two principal elements : A E, the registering apparatus, and A S, the sphygtno- 

 graphic apparatus, that is to say, which receives, transmits, and amplifies the movements which are to be 

 studied." The compression exerted upon the bag c, which is placed over the apex of the heart between the in- 

 tercostal muscles, is conducted by the tube t c, which is filled with air, to the first lever. The compression ex- 

 erted upon the bags o and , in the double sound, is conducted by the tubes t o and tv to the two remaining levers. 

 The movements of the levers are registered simultaneously by the cylinders A E. 



with the double sound for the right auricle and ventricle, and one is connected with the 

 bag destined to receive the impulse of the heart. In an experiment upon a horse, every 

 thing being carefully arranged in the way indicated, the clock-work was set in motion, 

 and the movements of the three levers produced traces upon the paper which were 

 interpreted as follows : 



1. The paper was ruled so that each division represented one-tenth of a second. The 

 traces formed by the three levers indicated four revolutions of the heart. The first revo- 

 lution occupied 1 T V sec., the second, 1^ sec., the third, 1^ sec., and the fourth, 1 sec. 



2. The auricular systole, as marked by the first lever, immediately preceded the ven- 

 tricular systole, and occupied about two-tenths of a second. The elevation of the lever 

 indicated that it was much more feeble than the ventricular systole, and sudden in its 

 character ; the contraction, when it had arrived at the maximum, being immediately fol- 

 lowed by relaxation. 



3. The ventricular systole, as marked by the second lever, immediately followed the 

 auricular systole, and occupied about four-tenths of a second. The almost vertical direc- 

 tion of the trace and the degree of elevation showed that it was sudden and powerful in 



