CULTIVATION OF TUBERCLE BACILLUS. 259 



Tubercular tissues always contain the bacilli or their 

 spores, and are always capable of reproducing the dis- 

 ease when introduced into the body of a susceptible 

 animal. From the tissues of this animal the bacilli 

 may again be obtained and cultivated artificially, and 

 these cultures are capable of again producing the 

 disease when further inoculated. Thus the postulates 

 which are necessary to prove the etiological role of the 

 organism in the production of this malady are all ful- 

 filled. 



The Tubercle BacilIjUS. — Of the three pathogenic 

 organisms liable to occur in the sputum of a tuberculous 

 subject, the tubercle bacillus will give us most difficulty 

 in our eiForts at cultivation. 



It is, in the strict sense of the word, a parasite and 

 finds conditions entirely favorable to its development 

 only in the animal body. On ordinary artificial media 

 the bacilli taken directly from the animal body grow 

 only very imperfectly or in many cases not at all. 

 From this it seems probable that there is a difference 

 in the nature of individual tubercle bacilli — some ap- 

 pearing to be capable only of growth in the animal 

 tissues, while others are apparently possessed of the 

 power to lead a limited saprophytic existence. It may be, 

 therefore, that those bacilli which we obtain as artificial 

 cultures from the animal body are offsprings from the 

 more saprophytic varieties. At best, one never sees 

 with the tubercle bacillus a saprophytic condition in 

 any way comparable to that possessed by many of the 

 other organisms with which we have to deal. 



In efforts to cultivate this organism directly from the 

 tissues of the animal, the method by which one obtains 

 the best results is that recommended by Koch — cultiva- 



