226 Manual of Veterinary 3jicrohiology. 



Sowing of tuberculosis of mammals directly upon 

 agar failed of results in the hands of MM. Straus and 

 Gamaleia. and even transference of serum cultures 

 on to agar only succeeded well after four or five pas- 

 sages on the serum. 



The bacillus, therefore, requires to become accli- 

 mated on an artificial medium in order to obtain a 

 vigorous growth. If it is then transferred to animals 

 it vegetates satisfactorily. 



The appearance of cultures on agar resembles that 

 of serum cultures. 



In the case of avian tuberculosis much richer cul- 

 tures are obtained directly upon serum. These cul- 

 tures begin by rounded, whitish spots, waxy and 

 moist, which after a few transfers produce a continu- 

 ous layer of the same appearance, thus contrasting 

 with the meager and dry film of human tuberculosis 

 (Straus and Gamaleia). Cultures on agar and on 

 bouillon are also more readily obtained and more 

 abundant than in the case of human tuberculosis. 



In bouillons, after a few days, small flakes appear 

 which gradually increase in size and fiill to the bot- 

 tom of the liquid without becoming dissociated ; they 

 break up into finer particles only when the vessel is 

 shaken. 



The tubercle bacillus also vegetates on potato, al- 

 though this is not a very favorable medium for its 

 growth. 



Research and coloration. — Koch's bacillus fixes color- 

 ing matters with difficulty and hence requires pro- 

 longed exposure. In order to abbreviate the opera- 

 tion recourse is often had to heat. The coloration, 

 however, if slowly obtained, is persistent even against 



