JOHN S. FULTON, M. D. 149 



The preposterous relations of sickness and mortality in child- 

 hood and infancy, on the other hand, are associated with known 

 phenomena of certain infections. After-coming morbidity max- 

 ima are characteristic of whooping cough, measles, diphtheria, 

 and scarlet fever. When we descend the scale of age from 12 

 years, we find, in passing from group to group (reading back- 

 ward), that mortality increases rather slowly, while concurrent 

 non-lethal sickness, rising more rapidly, soon develops a spurt. But 

 the pace of mortality is steadily mended until, below the age of 

 five years, a winning spurt of mortality is developed. Traveling 

 backward in this way, with each younger group we enter a zone 

 of less vital resistance and larger numbers. Communicable sick- 

 ness must inevitably be increased in passing from group to 

 group in the direction of larger numbers and smaller immunity, 

 unless the action takes place in a medium presenting another 

 kind of resistance, which increases at a rate superior to the 

 numerical increment and the declining immunity. 



The paradox will be solved if we can show that in passing 

 from one group to the next younger we enter a space which is 

 less infectible. The period of school attendance is spent in a 

 bounded space of relative isolation, a sociologic inclusion within 

 which are many segregations according to age, and more strin- 

 gent in younger groups, as the power of locomotion and asso- 

 ciation is less. The oldest group, leaving school, enters a more 

 infectible space; and the youngest group, entering school, leaves 

 a space less infectible. 



The heavier incidence of measles, scarlet fever, and diph- 

 theria on the first two years of school age, and the behavior of 

 the sickness curves in vacation, testify that a space-equivalent 

 of immunity is lost on entering school. Below school age the 

 space relations of children grow narrower and less infectible 

 until, at the beginning of the third year the curve of childish 

 mortality piles up like a wave at a breakwater. It is a difficult 

 thoroughfare to the isolated space of babyhood, which in its 

 earlier divisions encloses no community, but a great number of 

 solitary infants. 



The after-coming morbidity maximum of childhood is easily 

 understood when we realize that these space-equivalents of im- 

 munity have no relation to vitality and therefore no power be- 

 yond the moment of attack. The value of these limited inhib- 

 itions is nevertheless very great. They restrain more and more, 

 in the descending age groups, the mediations of sickness be- 

 tween members of the group, so that attack rates may appear to 

 decline while fatality rates are increasing. Notwithstanding the 

 extreme sensitiveness of the infant organism, epidemics of child- 

 hood can not project into infancy more than a sporadic morbidity, 



