BIOLOGICAL PRODUCTS (VETERINARY). 
073 
cinated frequently, every three to four months if possible. After 
one year of age vaccination gives protection for five or six 
months. Cattle older than two and a half years very seldom need 
to be treated, especially if they were vaccinated when calves. As 
the vaccine produces immunity by giving the animal a mild form 
of the disease, it is advisable not to vaccinate if the animal is 
already exposed or suffering from the disease. Nor should they 
be vaccinated- if they are suffering from any debilitating disease 
or in poor condition resulting from shipping, driving or lack of 
feed or care. Vaccinating at the time of dehorning or castrat¬ 
ing, or during cold or stormy weather, is not recommended. 
Blackleg vaccination is now generally recognized as an 
efficient and reliable means for the prevention of blackleg. It 
has done much towards reducing the prevalence of the disease. 
Occasionally an animal treated with the vaccine dies from the 
results of the inoculation, but the number of such fatalities is so 
small as to become a negligible quantity when compared with 
the great protective value of the vaccination. 
Rabies Vaccine. In 1885 Pasteur devised a vaccine for the 
prevention of rabies in the human which has given very satisfac¬ 
tory results. Owing to the complicated nature of the treatment, 
it has not been employed in veterinary medicine until quite re¬ 
cently. The treatment consists of a series of vaccinations with 
rabies virus of a known degree of attenuation. In the preparation 
of the vaccine, rabbits are inoculated with a fixed virus, that is 
one that has reached its maximum degree of virulence for the 
species. Death usually occurs in the rabbit in six or seven days. 
Its spinal cord is then removed in its entirety and submitted to a 
process of desiccation by suspending it over caustic soda or 
potash at a temperature of 22 c.c. for a definite period. In ad¬ 
ministering the vaccine the patient is first given an injection of 
the virus that has been attenuated for a week or more. Each suc¬ 
ceeding dose consists of virus that has been attenuated less and 
less until the animal has reached such a stage of immunity that 
it can withstand unattenuated virus. 
Reports indicate that the method is attended with the same 
degree of success as in dealing with rabies in man. 
