292 BACTERIA AND DISEASE 



ample ground for concluding that the sanitary circumstances of a 

 town may be such as to depress the physical vitality of children, and 

 lessen their powers of resistance to infectious disease once introduced 

 among them. Thus the insanitary conditions named weaken the 

 physique of the children, as well as preparing favourable external 

 circumstances for the growth and multiplication of the germs of 

 disease. Hence it must come about that from time to time a disease 

 like diphtheria will take on an increased virulence as well as a higher 

 measure of epidemicity. 



But general conditions do not wholly account for the occurrence 

 of diphtheria. Apart from these general conditions personal infection 

 is the chief means by which diphtheria is spread. 



Infection has been proved to be conveyed by nasal discharge of 

 infected persons, or by kissing infected persons, or by sucking sweets, 

 pencils, pens, slates, and other articles in schools. School influence 

 as an agency in the dissemination of diphtheria was shown as far 

 back as 1876 by Mr W. H. Power, and since that date abundant con- 

 firmatory evidence has been forthcoming. In 1894 Mr Shirley 

 Murphy, medical officer to the London County Council, reported 

 that there had been an increase in diphtheria mortality in London 

 at school ages (three to ten) as compared with other ages since the 

 Elementary Education Act became operative in 1871 ; that the 

 increased mortality from diphtheria in populous districts, as com- 

 pared with rural districts, since 1871, might be due to the greater effect 

 of the Education Act in the former ; and that there was a diminution 

 of diphtheria in London during the summer holidays at the schools 

 in 1893, but that 1892 did not show any marked changes for August. 

 In 1896 Professor W. E. Smith, the medical officer to the London 

 School Board, furnished a report* on this same subject of school 

 influence, in which he produced evidence to show that the recru- 

 descence of the disease in 1881-90 was greatest in England and 

 Wales at the age of two to three years, and in London at the age of 

 one to two years, in both cases hefore school age; that age as an 

 absolute factor in the incidence of the disease is enormously more 

 active than any school influence, and that personal contact is another 

 important source of infection. 



Although it is said that " statistics can be made to prove 

 anything," there can be little doubt that both of these reports 

 contain a great deal of truth ; nor are these truths wholly incompatible 

 with each other. They both emphasise age as a great factor in the 

 incidence of the disease, and whatever affects the health of the child, 

 population, like schools, must play, directly or indirectly, a not 

 unimportant part in the transmission of the disease. 



* Jour, of State Med., 1896, vol. iv., p. 169; see also L.C.C. Education Beport, 

 1904, No. 718. 



