126 BIOLOGY OF DEATH 



female group. By the fifth year of life, the specific rates 

 of mortality chargeable to reproductive organs have 

 dropped in both sexes practically to zero, amounting to 

 less than 0.01 per thousand exposed to risk. At about 

 the time of puberty the female curve begins to rise and 

 goes up very steeply. By age 30 it has reached a value 

 of 1 per thousand exposed to risk. From that point the 

 force of this specific mortality rises slowly, but at a 

 practically constant rate, to extreme old age. The male 

 curve is in striking contrast to the female. From about 

 age 20 it rises steadily, at an almost constant rate of 

 increase, but a much slower one than the female, until 

 the end of the life span. It crosses the female curve — in- 

 dicating a higher specific rate of mortality from break- 

 down of the reproductive organs in men than in women — 

 for the first time at about age 78. This is, of course, the 

 time of life when disturbed functioning of the prostate 

 gland in the male begins to take a relatively heavy toll. 



Figure 31 shows specific rates of mortality from 

 breakdown of the kidneys and related excretory organs. 

 Death from these causes is relatively infrequent in in- 

 fancy and early childhood. The low point is reached, 

 as in so many of the other cases, at about the time of 

 puberty. From then on practically to the end of the 

 span of life the specific force of mortality from excretory 

 failure increases at an almost constant rate. During 

 the reproductive period, from about 15 to 45 years of age, 

 specific rates of mortality from these causes are higher 

 in the female than in the male. After that point the male 

 curve is higher. The relatively heavy specific mortality 

 of the female in early life is undoubtedly due to the heavy 

 strain put upon her excretory organs by child-bearing. 



The specific force of mortality from breakdown of 



