1 70 THOMPSON YATES LABORATORIES REPORT 
other hand, as Nature intended it to be given, is never once exposed to air, passing 
directly and at the time of its manufacture in the gland, to the stomach of the young 
animal, and, apart from the possibility of disease in the gland, is bacteriologically 
clean and pure. 
Sterilization, valuable as it is as a final safeguard against tuberculosis, is after 
all only an expedient, and must not be put into so much prominence that the 
importance of the safeguard afforded by keeping the cows healthy is lost sight of, 
although we cannot take it for granted, in considering the merits of different methods, 
that essential accessories common to them all will be observed. The one merit of 
sterilization is that it is an expedient easy of application and presenting few adminis- 
trative difficulties. Beyond any question the ultimate advantage lies in obtaining the 
milk from herds free from tuberculosis. It is, in fact, comparable with the advantage 
of obtaining drinking water from a pure source, instead of taking it from a 
contaminated one and relying upon purification afterwards. The first aim must be 
to ensure that the source of the milk is pure ; in other words, that the cows are free 
from tuberculosis, or if this, under existing conditions of the law and public opinion, 
is unattainable, that they shall at least be free from any tuberculous disease of the 
udder, or any tumour or condition of the udder simulating tuberculous disease, or, 
having regard to difficulties in diagnosis, we may with advantage go even a step 
further, and demand that the udder in all cows from which milk is taken for human 
food shall be in a perfectly normal condition. 
The main causes of tuberculosis in cows are notorious : close confinement in 
ill-ventilated, badly-lighted, ill-constructed and dirty cowsheds — defects all as easy to 
remedy as is removal from the cowshed of the obviously tuberculous animal before 
it can cause infection of the rest. 
In the city of Liverpool about 26,000 gallons of milk are consumed every 
day ; one-half of it comes from cows, about 6,000 in number, kept within the city, 
the other half comes from cows kept in the country, and is sent in by rail. Within 
recent years that part of the milk supply which comes from cows kept within the city 
has been practically free from tuberculosis. This has been brought about by the 
sanitation of the cowsheds, adequacy of air, light, and cleanliness, by systematic and 
frequent inspection of the cows by qualified inspectors with veterinary help, by 
frequent bacteriological analysis of the samples of milk : these are the measures which 
have effected this end. I do not say that out of the 6,000 cows in the city there is 
not a single one affected with tubercle, but merely that there are few with such forms 
of tuberculous disease as would be likely to contaminate the milk supply. 
These methods and this system of inspection were not initiated without 
difficulty and opposition. There is no opposition now ; every person acquiesces in 
advantages which have been gained. But there is another aspect to the question. 
Only one half of the quantity of milk consumed in Liverpool is supplied from the 
