From these figures the extraordinary increase during the last few years is clearly demonstrated.
Sir Richard Thorne Thorne, in 1891, drew attention to the influence of damp soils and schools upon diphtheria. 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 compared 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. R. Smith, the Medical Officer to the London School Board, furnished a report[96] on this same subject of school influence, in which he produces evidence to show that the recrudescence 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 before 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 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.
The Pseudo-diphtheria Bacillus.[97] Löffler and Hoffman described a bacillus having the same morphological characters as the true Bacillus diphtheriæ, except that it had no virulence. Roux believes this is merely an attenuated diphtheria bacillus. It is frequently found in healthy throats. The chief differences between the real and the pseudo-bacillus are:
1. The pseudo-bacillus is thicker in the middle than at the poles, and not so variable as the Bacillus diphtheriæ. Polar staining is absent.
2. Its growth on potato reveals cream-coloured colonies visible in a couple of days; the real bacillus is invisible.
3. The pseudo-bacillus will not grow at all anaërobically in hydrogen, but the Bacillus diphtheriæ is able to do so.
4. There is the great difference in virulence.