BIOLOGY IN HUMAN AFFAIRS 



of the blood pressure, while the heart is contracted and 

 while the heart is relaxed. 



At first everyone was concerned largely with the question 

 of high blood pressure, but now it is recognized that either 

 high or low blood pressure may be of diagnostic impor- 

 tance. Life insurance companies have given particular 

 consideration to this question, and to-day the determina- 

 tion as to the life expectancy of an individual may rest 

 largely on an exact determination of his blood pressure. 

 The majority of medical directors of insurance companies 

 are inclined to think that pressure somewhat below the 

 average predisposes the individual to increased longevity. 

 Pressure very much above the average is serious. These 

 observations represent the fundamentals of our knowledge 

 of the blood pressure, but do not begin to represent all 

 of the knowledge that scientific medicine must have before 

 it is able to render unequivocal judgments in this field. 



Since the factors that control blood pressure are numer- 

 ous and include not only purely physical factors but also 

 mental and emotional conditions; since the part played 

 by heredity is not certainly known; and since the influence 

 of proper elimination from the kidneys, of the amount 

 of fluid and of salt taken into the body, and of alcohol 

 and tobacco, is not certainly established, there is a wide 

 field of research on this frontier of medicine still available 

 to the explorer. 



It is believed that alcohol in moderation does not in- 

 fluence the blood pressure in some people. The withdrawal 

 of excessive amounts of alcohol will lower the blood pres- 

 sure in some people, but in others it apparently will not 

 have this effect. Because of the food qualities of alcohol, 

 it tends to favor putting on weight; and it has been estab- 

 lished by insurance statistics that excess weight after 

 middle life is likely to be associated with higher blood 

 pressure. 



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