302 BACTERIA PATHOGENIC TO MAN 



per cent, of cadavers show the healed lesions of tuberculosis. The 

 small proportion of these which progressed to serious lesions or became 

 reinfected indicate a degree of acquired immunity. Artificial im- 

 munity is an attempt to imitate nature's methods, and is obtained 

 by the inoculation of a modified living culture or of toxins and dead 

 bacteria. The injection of toxins, as in Koch's tuberculin treatment, 

 produces in animals a certain degree of acquired resistance to larger 

 doses of toxins, but does not protect to any appreciable degree from 

 subsequent living tubercle bacilli, or produce in animals an antitoxic 

 serum. In 1892 Trudeau succeeded in producing in rabbits an appre- 

 ciable immunity by inoculations of living avian cultures. The rabbits 

 so treated supported, as a rule, inoculation of virulent tubercle bacilli 

 in the anterior chamber of the eye, while in controls the eyes were 

 invariably lost. Later, attenuated human cultures were used with the 

 same results. De Schweinitz, McFadyan, Behring, and Pearson Gilli- 

 land have since reported successful results. The latter two treated a 

 number of cows by giving each of them seven intravenous injections of 

 1 to 6 c.c. of an emulsion of tubercle bacilli. This was of an opacity 

 equal to a twenty-four-hour broth culture of typhoid bacilli. They 

 report from their investigations 1 that the treatment had the effect not 

 only in keeping in check the progress of the tuberculous process, but 

 of causing in some cases a distinct retrogression. The bacilli remained 

 alive in the encapsulated lesions. 



The work already done is believed by Trudeau to establish the 

 principle that in order to be successful the protective inoculation must 

 be made with living germs of such diminished virulence for the animal 

 experimented upon as to produce a reaction ending in healing of the 

 process at first set up by them. This is termed by Behring isopathic 

 immunity. 



The avian and bovine bacilli immunize against infection from human 

 bacilli equally as well as the attenuated human variety. This is strong 

 evidence in favor of the genetic unity of all tubercle bacilli. Up to 

 the present time the results in animals hardly permit the inoculation 

 of man with living bacilli for purposes of producing immunity. The 

 practical difficulties which confront one make it at present probably 

 unadvisable to use such methods in cows except in an experimental 

 way. 



The serum of animals treated with bacilli and their products has 

 not given curative results. 



Among the numerous medicinal agents that have been tried without 

 avail to protect animals against the action of the tubercle bacillus 

 may be mentioned tannin, menthol, sulphuretted hydrogen, mercuric 

 chloride, creosote, creolin, phenol, arsenic, eucalyptol, etc. 



Agglutination. The results obtained by various observers has been 

 very conflicting. Two methods are employed in making the test. In 

 one a vigorous growth of bacilli is dried, ground up and an emulsion 



i University of Pennsylvania Medical Bulletin, April, 1905. 



