2 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



successful vaccine must be attenuated to the point which repre- 

 sents a happy medium, and which clearly indicates both safety and 

 activity. Some of the more common methods used in attenuating 

 viruses are attenuation by passage of the virus through some species 

 other than the animal for which the virus is specific (smallpox vac- 

 cine); attenuation by drying at constant temperature (rabies vac- 

 cine, Pasteur) ; attenuation by growth at a temperature above the 

 optimum (anthrax vaccine) ; and attenuation by chemicals. 



Some of the more important vaccines are smallpox vaccine, black- 

 leg vaccine, rabies vaccine and anthrax vaccine. 



Bacterial vaccines or bacterins consist of suspensions of young, 

 living cultures of specific bacteria which have been killed chemically 

 or by the application of moist heat at a temperature slightly above 

 their thermal death point. Wright and Douglas first advanced the 

 theory of opsonic action and suggested that the subcutaneous injec- 

 tion of a given species of bacteria which had been killed, conferred 

 to the blood of the treated individual greater opsonic activity towards 

 the species of organisms in question. The opsonic activity is ex- 

 pressed by the degree of readiness with which the phagocytes destroy 

 invading micro-organisms. Bacterial vaccines may be used in the 

 form of autogenous or stock vaccines. An autogenous or " personal " 

 vaccine is one prepared from a culture of the specific organism iso- 

 lated from the patient in question. Stock bacterial vaccines are pre- 

 pared from stock cultures of the various organisms. The latter may 

 be manufactured and stored until required for treatment. Some of 

 the more common 'bacterial vaccines are typhoid (especially as a 

 prophylactic), streptococcus, staphylococcus, streptococcus and 

 staphylococcus combined, gonococcus, pertussis, acne, colon, canine 

 distemper and equine influenza. 



Tuberculins are preparations made from the human and bovine 

 strains of Bacterium tuberculosis and are used both in diagnosis and 

 treatment. Koch's Tuberculin (Old) is the concentrated, glycer- 

 inated beef bouillon, in which the tuberculosis organism has been 

 grown. The active substance of the Tuberculin, which is appar- 

 ently an albuminous derivative insoluble in alcohol, is elaborated 

 by the organisms during their multiplication. In human, as well as 

 in veterinary practice, Tuberculin may be applied as a diagnostic 

 agent in various ways. In addition to the hypodermatic injection of 

 Tuberculin Old, the methods of Calmette, von Pirquet and Moro 

 may be used. Calmette's 'test consists in the instillation in the eye 

 of Koch's Tuberculin Old which has been prepared by precipitating 

 and washing the resulting precipitate. Von Pirquet's reaction de- 



