THE CAUSES OF DEATH 121 



mortality from breakdown of the respiratory system. 

 The male curve rises in nearly a straight line, while the 

 female curve lies far below it, and actually shows a point 

 of inflection at about age 45, becoming for a short period 

 convex to the base. The explanation for the great sep- 

 aration of the two curves in this period is probably fun- 

 damentally occupational. From the nature of their 

 activity males, during this period of life, are probably 

 subject to a greater risk of breakdown of the respiratory 

 system than are the more protected female lives. From 

 age 70 on, both curves ascend with increased rapidity, 

 the female curve rising above the male, presumably in 

 compensation for the marked dip which it exhibits in mid- 

 dle life. It is, of course, well known that respiratory 

 mortality bears heavily upon the aged. 



The next group which we shall consider has to do 

 with deaths from breakdown of the primary and second- 

 ary sex organs. This cause group furnishes an ex- 

 tremely interesting pair of curves shown in Figure 30. 

 Before discussing in detail their form, a word of explan- 

 ation as to their makeup should be given. This may 

 best be done by exhibiting and discussing for a moment 

 the causes of death which are included in this group. 

 Table 10 shows the data. 



In this rubric are included "Premature birth" and 

 "Injuries at birth." The question at once arises, why 

 should these two items, "Premature birth" and "Injuries 

 at birth" be included with the primary and secondary sex 

 organs, since it is obvious enough that the infants whose 

 deaths are recorded under these heads in the vast major- 

 ity of cases, if not all, have nothing whatever the matter 

 with either their primary or secondary organs? The 

 answer is, in general terms, that on any proper biological 



