96 BIOLOGY OF DEATH 



curve, exhibiting great variability. The third compo- 

 nent is made up by the deaths of youth. This accounts 

 for 50.8 deaths out of the total of a thousand, and its 

 range extends from about the time of birth to nearly 45 

 years. Its mid-point is between 20 and 25 years, and it 

 exhibits less variability than either the middle life or the 

 old age curves. The fourth component, the modal point 

 of which is at the point on the base of the diagram marked 

 4 covers the childhood mortality. It accounts for 46-4 

 deaths out of the total of 1,000. Its range and variability 

 are obviously less than those of any of the other three 

 components so far considered. The last, excessively skew 

 component, is that which describes the mortality of in- 

 fancy. It is given by a J shaped curve accounting for 

 245.7 deaths after birth, and an antenatal mortality of 

 605. In order to get any fit at all for this portion of the 

 mortality curve it is necessary to assume that the deaths 

 in utero and those of the first months after birth are a 

 homogeneous connected group. 



Summing all these components together it is seen 

 that the resulting smooth curve very closely fits the series 

 of small circles which are the original observations. 

 From the standpoint merely of curve fitting no better 

 result than this could be hoped for. But about its bio- 

 logical significance the case is not quite so clear, as we 

 shall presently see. 



Pearson himself thinks of these five components of 

 the mortality curve as typifying five Deaths, shooting 

 with different weapons, at different speeds and with dif- 

 fering degrees of precision at the procession of human 

 beings crossing the Bridge of Life. The first Death is, 

 according to Pearson, a marksman of deadly aim, con- 

 centrated fire, and unremitting destructiveness. He kills 



