188 STUDIES IN ADVANCED PHYSIOLOGY. 



plete circulation is about thirty-two seconds. Of this time 

 about nine seconds are lost in passing through the pul- 

 monary circulation, the other twenty-three through the 

 systemic . 



The real rapidity with which the blood moves may, 

 therefore, be readily appreciated from this when we remem- 

 ber that a corpuscle of blood might in the course of such a 

 short time as one hour carry 120 loads of oxygen to the 

 head. It means that the entire amount of blood in the body 

 is moved in a period of time no greater than one minute 

 twice over the entire course of circulation. If one should 

 fancifully try to calculate how many loads of oxygen on an 

 average a red corpuscle would carry in the course of a 

 month, the figures would no longer be comprehensible; 

 while if the calculation should be extended in computing 

 the actual distance which such a corpuscle had covered in 

 this vast number of trips the result might possibly be com- 

 prehended only when reduced to miles. 



In this connection it may be well to repeat that this 

 whirl of blood is mainly for the purpose of carrying in an 

 uninterrupted flow the supply of oxygen to all parts of the 

 body, and only incidentally to carry the nourishment and to 

 remove the waste, even though these two latter are, of 

 course, indispensable. 



THE PULSE. 



1. Cause of Pulse. The sudden injection of several 

 ounces of blood at each beat into the aorta causes the walls 

 of the aorta to be additionally distended right at the heart 

 in order to make room for this new amount. This expan- 

 sion at the origin of the aorta is made possible by the elas- 

 ticity of its wall. But by this elasticity the walls, distended 

 so suddenly, try to regain their original position, and in so 

 doing start a wave along the artery familiar to us all as the 

 pulse, much like a pebble thrown into the water will start 

 at that point a series of waves running in every direction. 

 Of course in the case of the aorta, the only direction possi- 

 ble is toward the periphery. 



