510 IMMUNITY AND PROTECTIVE INOCULATION 
of diseases of animals. There is some method known, proposed or 
being investigated for practically every infectious disease. The 
methods that are now in use, together with the diseases against which 
they are employed with sufficient success to warrant their recom- 
mendation, may be summarized as follows: 
Active immunity. This method is employed most extensively in 
immunizing cattle against Texas fever and bovine contagious pleuro- 
pneumonia. It is used in France to immunize against sheep pox 
(clavelization). 
Since the 18th century there has been practiced in France the 
artificial immunization of sheep by the inoculation of the virus of sheep 
pox just as the variolization of man was practiced before the discovery 
of small pox vaccine. In France, the law requires the inoculation 
(clavelization) of flocks in which sheep pox appears, but it interdicts 
the practice in unattacked flocks. 
The injection of animals with attenuated virus of the disease against 
which immunity is to be established. This method is used most 
extensively in anthrax, rabies, symptomatic anthrax and swine ery- 
sipelas. 
The practical value of vaccination for rabies (Pasteur treatment) 
over that of most other diseases, is the fact that it is effective if made 
early in the period of incubation. This method, which takes advan- 
tage of the long period of incubation in rabies, constitutes a means of 
handling an infectious disease intermediate between protective inocula- 
tion and a therapeutic treatment. 
A large amount of work has been done by many investigators to 
secure practical means for immunizing cattle against tuberculosis 
and horses against glanders but thus far satisfactory methods have 
not been formulated. 
Passive immunity. It is employed as a prophylactic in swine 
erysipelas, tetanus, diphtheria, hog cholera (serum alone method) and 
also in certain diseases such as rabies and anthrax for which there are 
also methods for active immunization. 
The use of the tetanus antitoxin to immunize horses against tetanus 
before subjecting them to operations, such as castration, or after 
receiving punctures of the skin or hoof (“farrier’s puncture’’) is 
becoming more and more prevalent in those countries and localities 
where tetanus is common. In France it seems to be used more than 
elsewhere. The serum is given in two injections from 10 to 12 days 
apart. Large animals receive 20¢.c. but small ones from 6 to 10c.c. 
at each injection. 
