HYGIENE OF BLOOD AND CIRCULATION 189 



dropping a key down the person's back rested on the fact that 

 the sudden chill causes the capillaries to contract. A piece of 

 ice applied for a few moments to the back of the neck will be 

 more likely to have the desired effect. Where bleeding con- 

 tinues after such simple treatment it is probable that some 

 small artery has been broken, or that the person's blood is in- 

 capable of clotting. An astringent is then advisable. Powdered 

 alum, tannin, or ferric chlorid may be applied on a tuft of cot- 

 ton. These substances cause the fine blood vessels to contract, 

 and thus stop the bleeding. In extreme cases a physician will 

 use adrenin, an extract of the glands lying close to the kidneys 

 (seepage 177). 



157. Increase in heart disorders. For a number of years past 

 the records show that there is a steady increase both in the num- 

 ber of people who die as a result of some defect or failure of the 

 heart and in the number of young people who suffer from some 

 form of heart trouble. The reasons for this condition are not 

 very clear. It is possible that one large source of heart trouble 

 among young people is the fact that improvements in the med- 

 ical arts have saved the lives of many boys and girls who would 

 otherwise have been killed by various common diseases, such 

 as scarlet fever and diphtheria. In many cases these diseases 

 leave as an after-effect a more or less serious injury to the 

 heart. Another source of heart trouble (besides the special dis- 

 eases) is in the poisoning of the system by bacteria that do not 

 cause special diseases. Decaying teeth, abscesses, and rheu- 

 matism would come in this class. Tobacco is known to cause 

 irregularity in the heartbeat in young people. There are also 

 strains and overwork for many people, as well as unsuitable 

 diet. Athletic enthusiasm in many cases leads to an over- 

 training of the heart. As a result the heart is either too strong 

 in proportion to the normal life of later years or leaves a need- 

 lessly large area exposed to injury. Defects of the heart are of 

 two types: (i) deterioration of the valves, usually resulting 

 from some infection or disease; and (2) a deficiency in the 

 muscle. 



