342 NATURAL TIIEOJ.OGY. 



action united in close relation to the condition of 

 the body. If the pulse is to be felt by the physi- 

 cian, the person must recline, for if he stand up, 

 on hydraulic principles a greater force is required 

 to move the upright column of blood, and the 

 heart beats more rapidly ; and this, especially, is 

 more remarkable, if the person be sickly and 

 weak. For the same reason, no physician feels 

 the pulse when his patient is anxious or perturbed, 

 or at least he must calculate on the pulse being 

 accelerated. These and many other examples 

 might be brought to show that the circulation al- 

 ters in correspondence with the position of the 

 body, and with its exercise ; and that it alters with 

 the emotions of the mind, as well as with the 

 changes in the position and movement of the 

 frame. We learn from this that the heart, through 

 its sensibilities, is the regulator of the circulating 

 system, and that it is for this purpose that it has 

 such extensive sympathies. These remarks we 

 premise as reminding the reader that there are 

 more things to be admired in the contemplation 

 of the living animal frame, than can be brought 

 under the head of the mechanism of the circulating 

 organs, or the adaptation of the tubes to the 

 known principles of hydraulics. It is, however, to 

 these that we must now beg his attention. 



