1 1 ELEMENTS OF PHYSIOL OGY 



187. The supreme, the transcendent importance to the 

 health of the tissues, of pure blood and good circulation, now 

 becomes apparent. All that the cells need, in order to be 

 sound and vigorous, is to have good food and oxygen 

 brought within their reach, and to have the waste material, 

 or products of combustion, removed ; the circulation meets 

 these needs. 



188. When unsoundness occurs in any part of the body, 

 there is a strong probability that the circulation there 

 is defective. The hair is lost by cutting off the circulation 

 from the scalp. The eyes may become inflamed, or the lids 

 diseased, because of obstructing in the neck the return 

 of the blood from the head; improper neck clothing or 

 stiffened muscles may cause this obstruction. A corn 

 grows on the toe because of the interruption of the circula- 

 tion there, resulting from intermittent pressure of the 

 upper leather of a tight shoe upon the toe as the foot 

 lengthens and shortens at every step. Indigestion may 

 result if vigorous mental or physical activity, just after 

 eating, draws the blood away and prevents the secretion 

 of the digestive fluids. Gout may occur from the deposit 

 of waste materials in the spaces around the joints where 

 the pressure from the circulation is least. Colds occur 

 when the blood vessels in the walls of the air passages be- 

 come congested or swollen with blood, and the vessels lose 

 their tone so that they cannot contract and keep the blood 

 moving onward. 



189. Pure Blood is just as necessary as free and unim- 

 peded circulation. We shall learn later how the digestive 

 organs serve to furnish the nutrition, how the lungs furnish 

 the oxygen, and how the skin, kidneys, and lungs remove 

 from the blood the impurities and waste materials. 



190. Taking Cold. Sudden or prolonged exposure to 

 cold while the muscles are inactive, so stimulates the sur- 

 face blood vessels through the vasomotor nerves that they 



