Jan, 6, 1876] 



NATURE 



183 



these viscera. A magnified view of this artificial heart, 

 into the cavities of which recording "ampoules" have 

 been introduced, is given in Fig. 2. 



As to the construction of the cams, M. Marey draws a 

 curve to represent the systole and diastole of the ventricle 

 of the actual heart, figuring it as a simple rise followed 

 by a less abrupt fall. He divides the linear horizontal 

 projection of this by twenty equidistant points, from 

 which he projects the same number of parallel vertical 



lines, or ordinates. Taking a small board he draws on it 

 a circle, from the centre of which radiate twenty equi- 

 distant lines, of which, when one has been measured off 

 so as to equal in length the first ordinate of the cardiac 

 horizontal curve, the others are made to correspond with 

 the second, third, &c. On uniting by a line the extre- 

 mities of these rays, a closed curve is the result, which 

 must form the edge of the cam c.v. The cam c.O. is 

 constructed in a similar manner from the auricular trace. 



Fig. I. 



When the cams are placed on the axle of the machine 

 in such a position that its rotation in one direction at a 

 certain speed produces a compression (or systolic move- 

 ment) by the auricular one at the interval of time before 

 that of the ventricular which elapses between the systoles 

 of the living auricles and ventricles, then the actual 

 cardiac revolution is correctly imitated both in this 

 particular and in the relative duration of the systoles 

 themselves. 



To verify^ the accuracy of the arrangements in the 



above-described schema, traces have been taken from it 

 similar to those from the auricles, ventricles, and arteries 

 of the horse. Fig. 2 illustrates the actual position, in the 

 artificial heart, in which the elastic ampoules (sacs filled 

 with air) which transmit its movements to recording levers 

 (Fig. 3) were placed ; and Fig. 4 is a simultaneous tracing 

 from the four, the fourth being that of the motion of the 

 heart-wall at E. The top curve is that from the auricle ; 

 the next is from the ventricle ; and the third from the 

 aorta. 



