JOHN S. FUIvTON, M. D. 



125 



In order to obtain larger numbers I have combined the experi- 

 ence of Berlin and Hamburg for four of the twelve monthly 

 groups, and have computed death rates per 1,000 survivors 

 through the first twelve months of life. The four groups com- 

 prise those born in December (16,547 births; 3,244 deaths in a 

 year), those born in January (17,825 births; 3,381 deaths in a 

 year), those born in June (15,735 births; 3,676 deaths), those 

 born in July (17,258 births; 3,760 deaths). 



Using the survivorship death rates as ordinates one can plot 

 four curves, two for summer and two for winter. By super- 

 imposing the January curve on the December curve, and the 

 July curve on that for June, one should have two figures in 

 each of which one should be able to define the limits within 

 w r hich should lie two new curves, fairly representing the chances 

 of life of winter-born infants, in one case, and of summer-born 

 infants, in the other. The formula of Karl Pearson will yield 

 death rates of the same sort from the beginning of pregnancy. 

 His data include males only, and mortality with respect to age 

 only. If his figures are correct, and if I have correctly divided 

 his three factors for periods of three months each into nine 

 factors for nine months, the death rates should yield a curve to 

 fit general experience with post-natal mortality at all seasons, 



