35.2 



Mr. A. H. Garrod on the Sphygmograph Trace. [May 19, 



while the interval between the beginning of the secondary rise and that of 

 the succeeding primary one constitutes the second part of the same trace. 



In 1865, Prof. Donders* published the results of experiments to de- 

 termine the relative duration of the first and second part of the cardiac 

 revolution with different rapidities of movements of the heart, taking as 

 his data the commencement of the first and second sounds respectively, 

 and he came to the conclusion that, though the second part varied with 

 the rapidity, the first part was almost constant in all cases. 



On commencing work with the sphygmograph, the author came to the 

 same conclusion with regard to the trace at the wrist, but, on improving 

 his methods of observation, he has arrived at a different result. 



The best means of insuring an accurate measurement of any sphygmo- 

 graph trace is to project all the points desired to be compared on to one 

 straight line, and this is done by fixing the trace on to a piece of board, 

 which has another pointed lever attached to it, with relations similar to 

 those of the lever and recording apparatus in the origiual instrument. By 

 this means lines can be scratched on the trace similar to those which 

 would be produced by the instrument itself if the watch-work were not 

 moving, and a result, as shown in Plate II. fig. 1, can be easily produced. 



The reason why this means has to be employed is, because the lever in 

 the sphygmograph moves in part of a circle, not directly up and down. 



The ratio between the length of the first part of each pulse-beat in a 

 trace and that of the whole beat was measured with a small pair of com- 

 passes, and from these the average was obtained, which thus eliminated, 

 in a great degree, the variations produced by the respiratory movements, 

 and also some of the clock-work imperfections. 



For example, in fig. 1, the ratios in the several beats are : — 



1 : 1-8 

 : 1725 

 : 1-725 

 : 1-775 

 : 1*725 

 : 1-7 

 : 1-725 

 : 1*775 

 : 1-8 

 : 1-775 

 : 1-675 

 : 1-75 

 : 1-75 

 : 1-725 



with an average of 1 : 1 *7443. 



* 11 On the Rhythm of the Sounds of the Heart." By F. C. Donders. Translated 

 in the ' Dublin Quarterly Journal of Medical Science,' Feb. 1868, from the 'Xederlan- 

 disch Archief voor Genees- en Xatuurkunde,' Utrecht, 1865. 



