360 HUMAN PHYSIOLOGY 



a large supply of blood is needed in the walls of the stomach and intestines 

 At this time, the arteries going to this region are dilated so as to receive 

 an extra supply. When the brain performs hard work, blood is supplied 

 in the same manner to that region. Hence, one should not study or do 

 mental work immediately after a hearty meal, for blood will be drawn away 

 to the brain, leaving the digestive tract with an insufficient supply. In- 

 digestion may follow as a result. 



The Effect of Exercise on the Circulation. — It is a fact familiar to 

 all that the heart beats more violently and quickly when we are doing hard 

 work than when we are resting. Count your own pulse when sitting quietly, 

 and then again after some brisk exercise in the gymnasium. Exercise 

 in moderation is of undoubted value, because it sends the increased amount 

 of blood to such parts of the body where increased oxidation has been 

 taking place as the result of the exercise. Exercise also affects the diameter 

 of the blood vessels because the sympathetic nervous system at this time 

 causes the muscular walls of the arteries to relax. Exercise should not be 

 attempted immediately after eating. This causes a withdrawal of blood 

 from the walls of glands of the digestive tract to the muscles of the body. 



Treatment of Cuts and Bruises. — Blood which oozes slowly 

 from a cut will usually stop flowing by the natural means of the 

 formation of a clot. A cut or bruise should, however, be washed 

 in a weak solution of carbolic acid or some other antiseptic in order 

 to prevent bacteria from obtaining a foothold on the exposed flesh. 

 If blood, issuing from a wound, is bright red in color and gushes 

 indistinct pulsations, then we know that an artery has been severed. 

 To prevent the flow of blood, a tight bandage must be tied between 

 the cut and the heart. A handkerchief with a knot placed over 

 the artery may stop bleeding if the cut is on one of the limbs. 

 If this does not serve, then insert a stick in the handkerchief and 

 twist it so as to make the pressure around the limb still greater. 

 Thus we may close the artery until the doctor is called, who may 

 sew up the injured blood vessel. 



The Effect of Alcohol on the Circulation. — Alcoholic drinks 

 affect the very delicate adjustment of the nervous centers control- 

 ling the blood vessels and heart. Even very dilute alcohol acts 

 upon the muscles of the tiny blood vessels, consequently, more 

 blood is allowed to enter them, and, as the small vessels are usually 

 near the surface of the body, the habitual redness seen in the face 

 of hard drinkers is the ultimate result. 



