8o A MANUAL OF PHYSIOLOGY 



for magnifying and recording the movements produced by 

 the cardiac impulse. Marey's cardiograph consists essenti- 

 ally of a small chamber, or tambour, filled with air, and 

 closed at one end by a flexible membrane carrying a button, 

 which can be adjusted to 

 the wall of the chest. 

 This receiving tambour is 

 connected by a tube with 

 a recording tambour, the 

 flexible plate of which acts 

 upon a lever writing on a 

 travelling surface a uni- 

 formly-rotating drum, for 



pvamnV - rnv^rpH with FlG ' I9- CARDIOGRAM TAKEN WITH 

 ,overed witn MAREY'S CARDIOGRAPH. 



Smoked paper. Any move- A, auricular systole; V, ventricular systole; 

 mpnt rnmmnmVatiaH tr D, diastole. The arrow shows the direction in 



ment communicated to which the tracing is to be read< 

 the button forces in the 



end of the tambour to which it is attached, and thus raises 

 the pressure of the air in it and in the recording tambour ; 

 the flexible plate of the latter moves in response, and the 

 lever transfers the movement to the paper. The tracing, 

 or cardiogram, obtained in this way shows a small elevation 

 corresponding to the auricular systole, succeeded by a large 

 abrupt rise corresponding to the beginning of the first sound, 

 and caused by the ventricular systole. This ventricular 

 elevation is the essential portion of the curve; it is alone felt 

 by the palpating hand, and the auricular elevation is often 

 absent from the cardiogram in man. The rise is maintained, 

 with small secondary oscillations, for about "3 of a second in 

 a tracing from a normal man, then gives way to a sudden 

 descent, that marks the relaxation of the ventricles, the 

 beginning of the second sound, and the closure of the semi- 

 lunar valves. An interval of about "5 second elapses before the 

 curve begins again to rise at the next auricular contraction. 



Such was the interpretation which Chauveau and Marey put upon 

 their tracings. Although neither their results nor their deductions 

 from them have escaped the criticism of succeeding investigators, it 

 is doubtful whether any adequate reason has been brought forward for 

 discarding them, and Chauveau has recently furnished fresh proofs of 

 their accuracy. The difficulties that beset the subject are great, for 



