ACTIVE IMMUNIZATION FOR THERAPEUTIC PURPOSES 655 



BLACKLEG 



Blackleg vaccine is used entirely as a prophylactic agent, for the 

 disease runs too acute a course for the vaccine to exert any therapeutic 

 influence. 



The vaccine is prepared by the Bureau of Animal Industry in the 

 following manner: The muscle tissue from a fresh blackleg tumor is 

 ground in a mortar, extracted or macerated with a little water, and 

 the fluid squeezed through cheese-cloth. The expressed fluid is then 

 evaporated at a temperature of 35 C. The dry brown scale is run 

 through a grinding mill and heated for six or seven hours at a temperature 

 of from 94 to 96 C. This process of heating attenuates the virulence 

 of the bacilli present so that, when injected, they produce but a mild 

 attack of the disease. The Department of Agriculture places the ground 

 material in packages containing a certain number of doses. These 

 packages are, upon request, mailed to veterinarians, who dilute the 

 ground muscle with as many cubic centimeters of sterile water as there 

 are doses in the package. One cubic centimeter of the suspension is 

 injected subcutaneously in some convenient area, as, e. g., about the 

 shoulders. 



Blackleg vaccine should be applied in the spring, before young cattle 

 are turned out to pasture on infected areas. 



In case of a fresh outbreak, all the healthy animals in the herd are 

 to be vaccinated as soon as possible. 



Blackleg vaccination has been fairly successful, and usually confers 

 an immunity lasting for a period of about six months. 



ACTIVE IMMUNIZATION FOR THERAPEUTIC PURPOSES; BACTERIAL 



VACCINE THERAPY 



Principles. Although bacterial vaccines have been extensively 

 employed in the treatment of various diseases, it is difficult to express 

 an opinion as to their real value, and it is altogether impossible to make 

 dogmatic statements as to the percentage of cases in which they will be 

 helpful or effect a cure, or as to what result may be expected in an in- 

 dividual case. Following Wright's original announcements, this special 

 therapy was enthusiastically received by the profession, and in a short 

 space of time the method was employed experimentally in many and 

 diverse infections. It may be stated that in many infections the vac- 

 cines may be beneficial, but they should be used only under proper 

 conditions, as was indicated in the first portion of this chapter. 



