AS TO SOUNDNESS. 149 



receives from the blood, and then to be expelled the 

 chest. 



This rhythm begins at the creature's birth and ends 

 only at its death. It must always be going on, but not 

 necessarily at the same rate. No rhythms in the body 

 are more variable than those of the respiration and cir- 

 culation, and so dependent are those two rhythms the 

 one on the other, that disturbance of either instantly 

 affects the other. In a state of health, and during tran- 

 quil moments, these rhythms bear almost an exact pro- 

 portion to one another, the rhythm of the lungs being to 

 the rhythm of the heart as one is to four, or in other 

 words, one respiration to four pulsations. We are sadly 

 too apt to overlook the interdependence of the two 

 rhythms 3 but as I shall show you, we cannot afford to do 

 so in the present instance. The blood of the entire body 

 has to pass through the lungs each time after it has been 

 sent through an organ or tissue, because its oxygen 

 carriers, the red corpuscles, have given up their oxygen 

 (which they can only get on passing through the lungs) 

 to the tissues, and the blood has received the waste 

 material which the tissue has done with. Seeing then 

 that the blood of the entire body must constantly, at 

 incredibly short intervals, be transmitted through the 

 lungs, and in the lungs exposed to the air, it is essential 

 that it should pass through them with ease and rapidity. 

 In the fleet subjects we are considering this is the more 

 necessary on account of the accelerated rhythm of the 

 heart and lungs induced by quickened motion of the 



