THE SPLIT PRODUCTS OF TUBERCLE BACILLUS 171 



wholly free from infection. Those of the third set had, 

 December 18, 30 mg., December 22, 75 mg., and December 

 26, 100 mg. of the precipitate residue. Half of this set died 

 before April 11 of tuberculosis, and the other half were 

 found to be tuberculous when killed on that date. To us 

 this indicates that the precipitate residue has some specific 

 effect upon tuberculous animals. We suspect that the ill 

 effect in these instances was due to the size of the doses, 

 because in reality the doses of the precipitate residue were 

 much larger than those of the cell residue much larger, 

 indeed, than the figures indicate, because, as we have 

 stated, the cell residue is not freely soluble in water, while 

 the precipitate residue is wholly soluble. In making up our 

 solutions we weighed out each residue and, in fact, the 

 animals received only the soluble parts of the amounts 

 stated in the figures. We can easily understand how exces- 

 sive doses given soon after inoculation with the avirulent 

 culture might induce such a result. This culture is aviru- 

 lent because it makes only an ineffectual attempt to grow 

 in the animal body. The feeble effort is resisted and over- 

 come by the natural defences of the healthy body. Now, 

 if these natural defences were wholly occupied in disposing 

 of the material injected, which should have been only 

 sufficient to awaken these defences, then the bacilli would 

 meet with no resistance and would multiply. 



The precipitate residue sensitizes guinea-pigs to the 

 tubercle bacillus just as the cell residue does. Evidently 

 our so-called residues are much alike, and it is more than 

 probable that they contain the same active constituent. 

 In cultures from three to six months old many of the bacilli 

 have undergone autolytic changes and the cellular sub- 

 stance has in part passed into solution. This is true of 

 both the poisonous and the non-poisonous groups . of the 

 protein that makes up the cell substance. Of one thing 

 we have satisfied ourselves at least, and that is that no 

 preparation from the tubercle bacillus should be used in 

 the treatment of tuberculosis until the poisonous group of 

 the tuberculous protein and other proteins in the culture- 



