On the alleged Increase of Cancer. 211 



possible to maintain the optimistic view tliat the whole of the apparent 

 increase can be thus explained ; and it must be admitted, as at any rate 

 highly probable, that a real increase is taking place in the frequency of 

 these malignant affections" 



It is evident, therefore, that although the view that the increase in 

 cancer was chiefly, if not entirely, apparent has, until recently, been 

 held in the English General Register Office, it is now reluctantly 

 accepted as a probable fact that cancer has really increased ; and it 

 must be admitted that the figures on which this conclusion is based, 

 as shown in the preceding table, look, at first sight, to be overwhelm- 

 ing in the weight of their evidence. 



A more careful investigation, however, shows that the ratios pre- 

 pared in the usual manner from the returns of the Registrar- General 

 at the best only approximately represent the truth, and that, in fact, 

 they may even be very misleading. Cancer is, par excellence, a disease 

 of mature life. In a population of 1,000,000 adult males, aged from 

 25 to 35, about 95 would die annually from cancer ; while there would 

 be about 2,530 deaths among 1,000,000 males from 55 to 65, and 

 4,405 deaths in 1,000,000 males aged from 65 to 75. Therefore, to 

 take the deaths from cancer at all ages in a community, and to com- 

 pare them with the total population in order to arrive at the cancer 

 death-rate, may introduce an error sufficiently serious to vitiate the 

 results. If there be a larger proportion of lives, below, say, 50 years 

 of age, the fraction formed by dividing the number of deaths from 

 cancer by the total population will give an unduly small ratio ; 

 whereas, if the lives above 50 years of age be in excess, the ratio will 

 be unduly large. Now the age distribution of one district may differ 

 materially from that of another, and the age distribution of the males 

 in a community may differ from that of the females, and the age dis- 

 tribution of the same district may possibly differ at different periods. 

 That this consideration is of great importance is shown by Table I 

 (Appendix), which gives the age distribution per million of population 

 of each sex according to the census of 1881 in the several divisions of 

 the United Kingdom. 



It will be noticed that the average age of females in England and 

 Scotland is higher than that of males, while the converse is the case 

 in Ireland ; and that the average age of the population in Ireland is 

 much higher than in either England or Scotland. Consequently the 

 death-rate from cancer given by the Registrar- Generals of the three 

 divisions of the United Kingdom in their Annual Reports are unduly 

 unfavourable to the female sex in Great Britain and to the male sex 

 in Ireland ; and similarly the death-rate from cancer in Ireland is 

 exaggerated as compared with that of the sister kingdom. 



To rectify this error it is necessary to assume a standard of age 

 distribution, to be applied to each set of statistics examined. It is not 



