FREQUENCY OF THE HEARTS ACTION. 215 



standing; and furthermore that the pulse is accelerated, in 

 the recumbent posture, when the body is only partially sup- 

 ported : 



"1. Difference between the pulse in the erect posture, 

 without support, and leaning in the same posture, in an 

 average of twelve experiments on the writer, 12 beats ; and 

 on an average of eight experiments on other healthy males, 

 8 beats. 



" 2. Difference in the frequency of the pulse in the recum- 

 bent posture, the body fully supported, and partially sup- 

 ported, 14 beats, on an average of five experiments. 



" 3. Sitting posture (mean often experiments on the writer), 

 back supported, 80 ; unsupported, 87 ; difference, 7 beats. 



" 4. Sitting posture with the legs raised at right angles with 

 the body (average of twenty experiments on the writer), back 

 unsupported, 86 ; supported, 68 ; difference, 18 beats. An 

 average of fifteen experiments of the same kind on other 

 healthy males gave the following numbers : back unsupport- 

 ed, 80; supported, 68; a difference of 12 beats." 1 



Influence of Exercise. It is a fact generally appreciated 

 that muscular exertion increases the frequency of the pul- 

 sations of the heart ; and the experiments just cited show 

 tli at the difference in rapidity, which is by some attributed 

 to change in posture (some positions, it is fancied, offering 

 fewer obstacles to the current of blood than others), is in 

 reality due to muscular exertion. Every one knows that the 

 action of the heart is much more rapid after violent exertion, 

 such as running, lifting, etc. Experiments on this point 

 date from quite a remote period. Bryan Robinson, who 

 published a treatise on the "Animal Economy" in 1734, 



1 TODD'S Cyclopaedia of Anatomy and Physiology, vol. iv., p. 188. There is 

 an apparent contradiction between these results, and results of the experiments 

 with the " revolving board." It is probable, however, that the subjects experi- 

 mented upon with the board were simply placed in the erect posture without 

 muscular effort, but maintained themselves in position without any aid. 



