544 IMMUNOLOGY 



rabbits to cage mates that had been infected with virulent organ- 

 isms. He determined by experiment tliat animals receiving 0.001 

 to 0.00001 mg. of highly virulent tubercle bacilli of the bovine 

 type develop progressive lesions and eliminate virulent organ- 

 isms. Normal animals v^^ere exposed to contact infection by plac- 

 ing them with cage mates thus infected. By means of a very 

 clever experiment in which a special type of animal cage was 

 used, he was able to show that normal animals and those having 

 nonprogressing lesions acquire infection with virulent bovine 

 tubercle bacilli under conditions in which the opportunity for 

 alimentary infection is eliminated. The i-esults of his experiments 

 may be summarized as follows: 



Summary of Lurie's Studies on Activi: Immunization.— 1. Of 

 the normal rabbits exposed to cage mates infected with virulent 

 bovine tubercle bacilli, 63.6 per cent contracted the disease within 

 six months and 73 per cent within one year. 



2. That the rabbits having a primary nonprogressive lesion 

 gained some immunity from the primary infection is indicated 

 by the fact that only 36.8 per cent of those exposed to cage mates 

 eliminating virulent bovine tubercle bacilli contracted infection 

 within six months and 60 per cent within one year. 



3. Since 27 per cent of the normal rabbits and 40 per cent of tlie 

 ones vaccinated with living human type tubercle bacilli escaped 

 infection, it would seem that natural resistance plays a very im- 

 portant role in immunity to tuberculosis. Lurie* points out that 

 vaccination saved only an additional 13 per cent. 



4. His results show that "vaccination reduced the incidence, 

 extent, and mortality of the disease, affected the route of infection, 

 changed its pathological character, and retarded its progress. The 

 disease acquired by vaccinated rabbits shared many characteristics 

 with adult type tuberculosis in man. ' ' 



Lurie's Investigation of the Mechanism of Immunity and the 

 Role of Allergy in Tuberculosis. — Lurie (1936, 1939) has stud- 

 ied the mechanisms of resistance and the role of allergy in normal, 

 tuberculous and vaccinated rabbits and guinea pigs. He intro- 

 duced agar impregnated with tubercle bacilli in the tissues. He 

 found that in normal animals the ])acilli grew unhindered in the 



♦Lurie: J. Exper. Med. 58: 305, 1933. 



