62 PHYSIOLOGY. 



fainted should be laid flat on his back, that the heart may 

 more easily drive blood to the brain. Many persons go to 

 sleep more readily while sitting than while lying down. 

 A sore hand feels less pain if held up, as in a sling, than 

 when hanging by the side, and a sprained ankle does 

 better rested on a chair, as less blood flows to it. Nearly 

 every one has noted the pain following the pressure of 

 blood when a sore hand, or foot, is suddenly lowered. 



Experiments illustrating the Effect of Gravity on Circulation. 

 Let all the pupils in the class stand. Let one arm hang freely by the 

 side. Hold the other arm straight up as far as the clothing will readily 

 permit. Observe : 



1. The difference in the color of the two hands. 



2. The difference in fullness, both in the feeling of fullness and in 

 the prominence of the veins. 



3. The difference in temperature; place the backs of the hands 

 against the cheeks. 



The position largely determines the amount of blood in the hand, and 

 the amount of blood determines the temperature, the size, and the color. 



The Heart Beat and the Pulse. i . 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, and divide by the 

 number thus reporting, to get the average. 



1 . Let all in the class count the pulse while sitting. Probably 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 immediately begin 

 to count the pulse. Compare with the pulse as taken while sitting. 



3. Compare the pulse before and after meals. 



