DIAGNOSIS OF TUBERCULOSIS 457 



Active immunization has been attempted with the following types 

 of preparation : 



1. Tuberculins. 



2. Vaccines. 



(a) Killed cultures. 

 (6) Soluble vaccines. 



3. Living tubercle bacilli. 



(a) Virulent organisms, Webb method. 

 (6) Attenuated viruses, 

 (c) Alien acid-fast bacilli. 



4. Sera. 



It has long been recognized that various tuberculins do not confer 

 immunity upon experimental animals, although in skilled hands they 

 possess undoubted curative value. 1 Killed cultures of tubercle bacilli 

 have not been satisfactory, and their use has been greatly restricted 

 by the non-solubility of the organisms which produce local indurations 

 of refractory nature. Soluble vaccines including "bacillus emulsions" 

 and various proteins of the bacillus do not appear to confer definite 

 immunity upon susceptible animals. The superiority of living viruses 

 over the various preparations of killed organisms and their products 

 for protective inoculation is conceded by the great majority of inves- 

 tigators. Webb and Williams 2 have attempted to induce artificial 

 active immunity in experimental. animals by injecting virulent tubercle 

 bacilli, beginning with one or two organisms and gradually increasing 

 the number. Their results, while few in number, appear to be worthy 

 of serious consideration. The use of attenuated cultures and of alien 

 acid-fast bacilli have not been successful up to the present time. 

 Sera have been equally unsatisfactory. 



Bovine Tubercle Bacillus. Cattle and swine are susceptible to 

 infection with the bovine tubercle bacillus and the disease is widespread 

 among dairy herds. Statistics indicate that in certain parts of the 

 United States the incidence of tuberculosis in swine increases almost 

 proportionately to the spread of the disease among cattle. This 

 condition is brought about partly through the practice of feeding 

 slaughter-house offal to swine, chiefly through dairies and cheese 

 factories where the skimmed milk or whey forms a not inconsiderable 

 part of the rations of swine. Scrofula or tuberculosis of swine thus is 

 a true ingestion disease. It is possible to infect swine by feeding human 



1 Trudeau, Osier's Modern Medicine, 1907, iii, 434. 



2 Jour. Med. Research, 1909, xx, 1; 1911, xxiv, 1. 



