164 ADVANCED PHYSIOLOGY 



conscious. If he can be placed flat on his back with the head 

 lower, if possible, than the rest of the body, blood will run 

 into the brain again, and the person regain consciousness. 

 While a fainting person may seem to need immediate attention 

 and help, the common tendency for everyone who is near 

 to rush to his relief is unfortunate. There is usually no 

 especial danger, and if two or three are waiting on the 

 patient others may much better remain quietly away, and 

 thus not prevent free circulation of air, about the patient, 

 who will doubtless very quickly recover. 



The Effect of Drugs upon the Circulation. The whole cir- 

 culation may be more or less profoundly modified by various 

 drugs, some of which increase and others decrease its action. 

 CafTein, for example, the active principle in coffee causes the 

 heart to beat more forcibly and at the same time causes a con- 

 striction of the small arteries so as to raise blood pressure. 

 For this reason it is called a stimulant. 



It has been frequently stated that alcohol increases the 

 activity of the heart. Careful experiment, however, shows 

 that not only is its effect not that of a stimulant, but that 

 when used in large amounts it very markedly weakens the 

 action of the heart. If taken in small amounts only, the 

 heart sometimes shows a slight increase in its rate of beating, 

 but this occurs only when the brain becomes excited, and if 

 the person is kept quiet no change in the heart beat is notice- 

 able. Its primary action is thus on the brain, as we shall 

 find later. 



A second effect of alcohol is more evident. The small 

 blood vessels in the skin are enlarged, probably from the 

 partial paralysis of the vaso-motor center. This produces 

 a flushed skin, a feeling of warmth and a false feeling of 

 increased circulation. Its result is to send more blood through 

 the skin with a consequent extra loss of heat. This action is 

 evidently not due to stimulation but to the relaxation of the 

 muscles and is thus a decrease of activity rather than an in- 



