292 Annual Report for 1908 of Royal Veterinary College. 
of the method. In no single instance has the vaccination 
caused any apparent injury to the animal’s general health. 
After the operation the calves have thriven as well as could be 
desired, and no vaccinated animal has developed any symptoms 
of tuberculosis. So much for the safety of the procedure. 
There remains, however, the equally important question 
whether any protection has been conferred on the animals by 
the operation. The most direct method of testing the value of 
any process of vaccination is to infect simultaneously an equal 
number of vaccinated and of natural or unvaccinated animals 
of the same age with a dose of infective material (tubercle 
bacilli in this case) certain to provoke serious results in the 
latter. Needless to say that heroic method could not be 
employed in dealing with very valuable pedigree stock, and 
one had to endeavour to measure the efficacy of the vaccination 
in another way, viz., by testing the vaccinated animals with 
tuberculin at a considerable interval (several months) after 
the operation. As judged in this way, the result of the 
vaccination has been highly satisfactory, in view of the fact 
that the vaccinated calves remained in contact with the cows, 
many of which were known to be tuberculous. Whereas in 
former years many of the calves born in the herd contracted 
the disease and reacted to tuberculin before they were a year 
old, nearly the whole of the animals which have been 
vaccinated have come successfully through the tuberculin 
test, and in the exceptional cases it is not improbable that the 
calves were infected before the vaccination, or shortly after- 
wards, before they had obtained the full degree of immunity 
which the operation confers. 
In referring to the results obtained in this herd it is not 
pretended that if they stood alone they would justify any one 
in recommending the method as one of proved safety and 
efficiency, but when they are known to be in harmony with 
the results obtained on much larger numbers of animals in 
other countries their value as an object lesson becomes much 
greater. 
Assuming, however, that this method of vaccinating calves 
against tuberculosis may now be regarded as practically devoid 
of danger, and efficacious up to a certain point, it must be 
confessed that the method has some important defects and 
limitations. The first of these is that the vaccination is useless 
in the case of animals already infected, and the second is that 
the protective effect is not obtained until two or three months 
after the vaccination. It follows from this that the vaccination 
may fail either because the calf was already infected before 
the operation, or because it contracts the disease within 
the following two months. A third defect is that the 
