106 
a 
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the money now devoted to beer. At the present time 
three times as much is spent by the British public on 
alcoholic drinks as on milk, and to this avoidable 
physiological impoverishment of the children, which is 
associated with the deficiency of milk, we can in large 
measure ascribe the proneness to catarrhs and the de- 
velopment of bronchitis, of rickets, and of tuberculosis. 
Early, then, in any attempts at practical reform 
must be placed the need for educating the public into 
willingness to buy more milk—at least twice or three 
times as much as is now being bought, for daily dietetic 
use. It follows that any measures proposed for the 
purification of milk must be tempered by consideration 
of the degree of risk to health, the administrative 
practicability of the proposals, and the expenditure 
involved. 
The necessity for milk sanitation, as for general 
sanitation, was first impressed on the public mind by 
the occurrence of epidemics attributed to contaminated 
milk. It was in 1857 that Dr. W. M. Taylor, of 
Penrith, traced an epidemic of typhoid fever to con- 
taminated milk, and ten years later he traced an 
outbreak of scarlet fever to milk. In 1880 Mr. Ernest 
Hart collected accounts of fifty epidemics of typhoid, 
fifteen of scarlet fever, and four of diphtheria traced 
to infected milk supplies ; and since then the number 
has become immensely greater, until, in recent years, 
commercial pasteurisation combined with a modicum of 
sanitary precautions on the farm and in the retailing 
of milk has been associated with a great decrease in 
the number of such outbreaks. In addition, septic 
sore throats have not infrequently been traced to milk 
derived from cows with udder inflammations; and, 
most important of all, a considerable proportion of 
human tuberculosis, especially in young children, has 
been attributed to milk. 
The history of the relation of human to bovine 
tuberculosis is an interesting chapter in bacteriology. 
In 1896 Theobald Smith announced that the tubercle 
bacillus of cattle differed materially from that of 
human tuberculosis. In rg0r Koch made the sensa- 
tional announcement in London that bovine tubercu- 
losis did not infect human beings. Inasmuch as, 
prior to this statement, the stress of anti-tuberculosis 
agitation had been much more against bovine than 
against human sources of infection, Koch’s dictum 
necessitated a re-investigation of the entire subject. 
A Royal Commission was appointed, and continued its 
inquiries for many years. The results of these and of 
many collateral investigations may be summed up in 
the statement that bovine tuberculosis undoubtedly 
does occur in the human being, but that it is a minor 
cause of human tuberculosis. Furthermore, that, 
unlike infection of human origin, bovine infection can 
NO. 2778, VOL. 111] 
NATURE 
[JANUARY 27, 1923 _ 
“ 
be effectively prevented—as can also the infection of — 
such occasionally milk-borne diseases as scarlet fever, 
typhoid fever, and diphtheria,—by pasteurisation of 
milk, or by bringing milk doméstically “just to the boil.” 
It was tuberculosis in the young subject which was — 
regarded as chiefly caused by milk infection, but — 
experimental observation of the type of bacillus found — 
in children’s tuberculous lesions has shown that less 
than one-third of tuberculosis in children under five ~ 
years of age is of bovine origin, the greater part being 
derived from infection of human source. The 
abdominal tuberculosis and tuberculosis of joints and 
bones and of glands, which may be due to infection 
of bovine source, are often not fatal; and it appears 
likely that, as Cobbett! has estimated, the mortality 
caused by infection with the bovine type of tubercle 
bacillus a¢ all ages is not more than six per cent. of that 
caused by bovine and human types of bacillus com- 
bined. This estimate was made several years ago. 
The proportion of human mortality from tuberculosis 
due to bovine infection is probably less now, for one 
of the striking features of tuberculosis mortality is its 
recent reduction at ages under five. Thus the death- 
rate from tuberculosis per million living at ages under 
five was 1213 in 1920, as compared with an average ] 
rate of 1883 in 1912-14. Inasmuch as only a relatively — 
small proportion of this mortality in the earlier period 
was caused by infected milk, the main credit for the 
decline, after making any needed allowance for changes 
in medical certification, must be given to the diminu- 
tion of human infection; and the entire result can 
reasonably be regarded as the joint product of measures 
for diminishing bovine tuberculosis, which, speaking 
nationally, have been on an extremely small scale, 
of measures for rendering bovine infection impotent 
(pasteurisation of milk and domestic heating), and of 
measures directed chiefly against human adult sources 
of infection. We have mentioned the six per cent. 
as a possible limit of the proportion of total tubercu- 
losis mortality at all ages which is due to bovin 
infection, without intention to minimise its importance, 
for the annihilation of tuberculosis of bovine origin 
would greatly reduce the mass of human suffering, and 
this end is within reach by easily practicable measures, 
which would serve the interest of dairymen as much as 
that of the consumers of milk. 
The possibility of acquiring tuberculosis or an 
acute infectious disease like scarlet fever, although the 
chief, are by no means the sole risks of contaminated 
milk. Past experience has shown an intimate associa- 
tion between an impure milk supply and excessive 
infant mortality ; and the remarkable reduction in = 

1L, Cobbett. ‘The Causes of Tuberculosis,” Cambridge University 
Press, 1917. 
