CONSTRUCTION AND USE OF A CARDIO-SPHYGMOGRAPH. 27 
5. ON THE CONSTRUCTION AND USE OF A SIMPLE Page 265. 
CARDIO-SPHYGMOGRAPH.* 
Ir is evident that a precise knowledge of the intervals between the 
main elements of the cardiograph and the sphygmograph trace must 
be of value in studying the hydrodynamics of the circulation of the 
blood; and a description will be here given of an instrument by which 
several results of interest have been obtained on this subject. 
This cardio-sphygmograph consists of a piece of board, 10 inches 
long by 54 inches broad, and is about half an inch thick, along one 
side of which one of Marey’s sphygmographs can be fixed, as shown 
in the accompanying figure. On the opposite to this is a spring (a), 
similar to that employed in the sphygmograph, which is attached toa 
movable support (b), so that its strength may be modified. A small 
ivory pad (c) is fixed to the lower surface of the free end of the spring, 
and this isin communication with the recording lever of the cardiograph 
apparatus by means of a silk thread (d). In this instrument the 
cardiograph lever (e) is very light, a little over two inches long, and 
connected to the board by means of a frame (/), which is just free of 
the movable part of the sphygmograph, when that is in position. The 
lever, which is one of the third system, is connected on either side, 
close to its fixed end, to two silk threads, one of which (d) is attached 
to the cardiograph spring, and the other to a small spring (g), which Page 266. 
moves it when it is less acted on by the stronger one. The apparatus 
is so arranged that the lever works perfectly when it is so placed as to 
be above the recording paper of the sphygmograph, when the latter is 
in position. The tip of the lever carries a steel pen (k). 
* “Journal of Anatomy and Physiology,” V. pp.-265-70. May, 1871. 
