PERSONAL AND CIVIC HYGIENE 



327 



Now since there were 32 deaths the week of Jan. 4, we take 

 such a part of the January column measured toward the right 

 on line OX as 4 days is a part of 31 days and make a tiny cross, 

 and measure up on the line OY ff of the height of the first 

 square and make another tiny cross. The first tiny cross lo- 

 cates a vertical line, or imaginary line, while the second cross 



Y 



JAN. FEE MCH. APR. MAY JUNE! JULY AUG. SEPT. OCT. NOV. 



O * X 



FIG. 83. Infant mortality curve, a, prevalence of flies; 6, diarrheals under 

 five years ; c, deaths under one year ; d, mean temperature. 



Scales 



1 c.m. = 50 deaths 

 1 c.m. = 200 fly prevalence 



1 c.m. = 10 degrees 

 1 c.m. = 15 days 



locates a horizontal line. At the place of crossing of these 

 two lines make another tiny cross. This cross indicates that 

 there were 32 deaths of children under 5 years of age during 

 the week of Jan. 4, 1908, in New York city. Next locate the 

 vertical line representing Feb. 1 and the horizontal line valued 

 at 26, and locate a second crossing point. 



Continue in this way, and connect all the tiny checks made 

 with an evenly curved line. This is called a " curve " and in 

 this case might be called a " diarrheal curve." Now take the 

 second line of data from the table and locate another curve. 



