S82 , MICROBIOLOGY OF SPECIAL INDUSTRIES 



to ten hours after treatment, continues for a few hours and finally 

 , subsides. Tuberculin (old) is used as a diagnostic agent in both human 

 and 'veterinary practice. 



Tuberculin (old) is prepared from cultures of the human or bovine 

 variety of Bad. tuberculosis. Apparently the active product can be 

 obtained ^ from attenuated as well as from virulent cultures. The 

 organism is inoculated into beef bouillon to which 5 per cent glycerin 

 has been added. The culture medium is usually distributed in flasks 

 and the tubercle organisms, when inoculated, are carefully placed on the 

 surface of the medium. The cultures are incubated at a temperature of 

 37° to 38° for six to ten weeks or longer, during which time a heavy 

 growth slowly spreads over the surface of the medium and finally falls 

 to the bottom of the flasks. In the successful preparation of tubercxiUn 

 it is important that the cultures should remain undisturbed, having 

 access to plenty of air, that the incubator temperature should be con- 

 stantly, maintained without fluctuations, and that the organisms should 

 be allowed to grow until they have completely elaborated the active 

 "tuberculinic" substance. After the growth is complete, the cultures 

 are removed from the incubator and sterilized in streaming steam. 

 The killed cultures are then evaporated over a water bath to one-tenth 

 the original volume, the bacteria are removed by passing the cultures 

 through paper and Berkefeld filter and a preservative is added. For 

 cattle the dose of tuberculin concentrated by evaporation to one-tenth 

 the original volume, is 0.25 c.c. to 0.7 c.c. Because of the fact that the 

 material is thick and syrupy in consistency and the dose is incon- 

 veniently small, it is usually diluted with seven parts of weak carbolic 

 acid solution. During the preparation it may be evaporated to four- 

 'fifths the original volume and preserved by the addition of i per cent 

 carbohc acid of sufficient volume to dilute properly so that each dose is 

 represented by 2 c.c. Two cubic centimeters of the diluted tubercuhn 

 is used as the dose for cattle. The product should be tested for activ- 

 ity by injecting known tuberculous animals with the tuberculin under 

 test. The presence of tj^pical reactions in tuberculous animals indi^ 

 cates the reliability of the product. 



In human, as well as in veterinary practice, tuberculin may be 

 applied as a diagnostic agent in various ways. In addition to the hypo- 

 dermic injection of tuberculin (old), as described above, the method of 



