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 
thythms ; but as I shall show you, we cannot afford to do 
so in the present instance. The blood ofthe 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 rapzdity. 
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 
