102 On l/ieLaws ofMortalil]/, and the Intensity of Human Life. 



duals remaining alive, out of the quantity supposed annually 

 to be born ; and secondly, the absolute quantity of the living, 

 at each year of age : which quantities constitute the distribution 

 of the whole comparative population just mentioned. 



Whilst the greater superiority of the selected class neces- 

 sarily produces the greater sum of permanent population, as 

 arising from any common radix of annual births, that relative 

 sum, also regulating the average of forthcoming years that 

 belong to each infant born, differs less, as regards the con- 

 tradistinguished sexes, than it does in case of lives of an in- 

 ferior qualit}'. If 2f years' difference in that average takes 

 place from one sex to the other, respecting a class selected as 

 'perfect, that quantity will extend to 3 years for a second class 

 to which the life-annuitants may be assimilated ; to ^\ for a 

 third class, or that of assurahle lives ; to 3| for the geneial ■po- 

 pulation of such countries as Great Britain or France, and 

 even to four years for the inferior qualities of lives amongst 

 that general population. 



The superior intensity, thus measured, of one class of lives 

 over another, without regard to difference of sex, is mostly 

 derived from the circuinstances that attend early stages of life. 

 When, on the contrary, infancy is subject to unfavourable con- 

 ditions of existence, no consideration of comparative healthi- 

 ness at subsequent ages, or of remarkable longevity amongst 

 the survivors, could afford any adequate compensation for the 

 curtailment resulting, in the population, from a deficiency of 

 wholesome subsistence, or of proper care towards the mainte- 

 nance of health, during infancy. In one country or district, 

 where those advantages are fully enjoyed, though from other 

 circumstances the rates of mortality should become very ele- 

 vated after the meridian of life is passed, the comparative po- 

 pulation growing out of an equal quantity of annual births, 

 maybe as three to two, with that of another country or district 

 in which infancy suflered privation and neglect; though from 

 advantageous circumstances of climate and soil in the latter, 

 the mortality proceeded at a very slow pace amongst the sur- 

 vivors, and the observation of facts tended to establish there 

 at very high rates the expectation of life in old age. This 

 again gives warning of the caution with which data, merely 

 local or circumstantial, ought to be admitted, and of the errors 

 likely to follow an extended application of them. 



Nevertheless, the data now possessed towards constructing 

 a law of mortality applicable to either sex and of any specific 

 class, are sufficient for obtaining very satisfactory results; pro- 

 vided they are judiciously employed, and that their compari- 

 son be governed by an attentive consideration of physiological 



principles. 



