On the other hand, milk is
undoubtedly a means of dissemination. Several outbreaks of an almost
explosive character, besides minor extensions of disease from one place
to another, have been traced to this cause. Milk may be contaminated in
various ways--at the dairy, for instance, or on the way to
customers,--but several cases, investigated by the officers of the Local
Government Board and others, have been thought to point to infection
from cows suffering from a diphtheritic affection of the udder. The part
played by aerial convection is undetermined, but there is no reason to
suppose that the infecting material is conveyed any distance by wind or
air currents. Instances which seem to point to the contrary may be
explained in other ways, and particularly by the fact, now fully
demonstrated, that persons suffering from minor sore throats, not
recognized as diphtheria, may carry the disease about and introduce it
into other localities. Human intercourse is the most important means of
dissemination, the contagion passing from person to person either by
actual contact, as in kissing, or by the use of the same utensils and
articles, or by mere proximity. In the last case the germs must be
supposed to be air-borne for short distances, and to enter with the
breath. Rooms appear liable to become infected by the presence of
diphtheritic cases, and so spread the disease among other persons using
them. At a small outbreak which occurred at Darenth Asylum in 1898 the
infection clung obstinately to a particular ward, in spite of the prompt
removal of all cases, and fresh ones continued to occur until it had
been thoroughly disinfected, after which there were no more. The part
played by human intercourse in fostering the spread of the disease
suggests that it would naturally be more prevalent in urban communities,
where people congregate together more, than in rural ones. This is at
variance with the conclusion laid down by some authorities, that in this
country diphtheria used to affect chiefly the sparsely populated
districts, and though tending to become more urban, is still rather a
rural disease. That view is based upon an analysis of the distribution
by counties in England and Wales from 1855 to 1880, and it has been
generally accepted and repeated until it has become a sort of axiom. Of
course the facts of distribution are facts, but the general inference
drawn from them, that diphtheria peculiarly affects the country and is