120 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



infection from a mechanical accident to some part of 

 a system of degenerated blood vessels, as from rup- 

 ture of a blood vessel in the brain or the plugging 

 of a nutrient artery to the heart. Or a degenerated 

 heart muscle may suddenly, without warning and 

 without discernible immediate cause, cease to beat, 

 or the kidneys, long overburdened, may quickly 

 cease their work and prove unamenable to any 

 therapeutic coaxing to renewed activity. Indeed, 

 among the aged we may regard as standard modes 

 of death these sudden vascular accidents of the brain 

 and allied circulatory failures in heart and kidney. 

 But in many instances the last days of life are 

 attended by bacterial invasions, often by several 

 kinds of bacteria, which are known to the pathologist 

 as terminal infections. These terminal infections, 

 making their way after some prostrating pathologi- 

 cal accident, or after an acute and specific infection, 

 such as pneumonia, are the quiet means of giving the 

 coup de grace to a mechanism no longer able to defend 

 itself. 



From this formidable array of physical dangers, it 

 is clear that to attain to sixty or seventy years of 

 age is in itself no mean achievement, especially if 

 these advanced years find the individual still free 

 from the burdens of invalidism. How does it happen 

 that of a hundred human beings that come into the 

 world, only a small number reach that record of 

 threescore and ten which the Bible has helped to 

 establish as a standard of respectable longevity? 



