OBSERVATION OF CIRCULATION. 49 



yields blood. We see a little blood oozing from the surface of 

 a fresh steak or roast. 



What kind of a substance is the blood ? Is it uniformly 

 distributed through the tissues, like water soaked up into a 

 cloth, or is it in distinct cavities ? Why is it so essential to 

 life ? How does it do its work ? 



Let us seek answers to these questions. 



EXTERNAL INDICATIONS OP THE CIRCULATION OP 

 BLOOD IN THE HUMAN BODY. 



The Heart-Beat and the Pulse. 1. The heart-beat, felt 

 at the left of the breast-bone. 



2. The pulse, felt at the wrist and at various parts of the 

 body. Perhaps the most convenient place to study it is at 

 the temple. Lay the forefinger lightly along the cheek just in 

 front of the ear. Count the pulsations for a minute. 



Let one or two pupils who are quick at figures step to the 

 blackboard and put down the number of pulsations of each 

 pupil as they are called, and divide by the number thus report- 

 ing, to get the average. 



1. Let all in the class count the pulse while sitting. Prob- 

 ably it will be best to discard the first trial, as there are likely 

 to be several failures from one cause or another. Then, too, 

 there is usually a slight excitement at the beginning of a 

 wholly new experiment. Get the average of the class. 



2. Find the pulse while sitting; rise quickly, and imme- 

 diately begin to count the pulse. Compare with the pulse as 

 taken while sitting. 



3. Again find the pulse after sitting quietly for some time ; 

 rise quickly, begin counting immediately, and note the num- 

 ber at the end of a half-minute, but count on continuously to 



