Bacilli Resembling the Tubercle Bacillus 759 



lations must be resorted to in cases of doubt, but as some of 

 these organisms sometimes kill the guinea-pigs after a 

 month or two, and as small nodules or tubercles may be 

 present in the mesentery, peritoneum, liver, lung, etc., of 

 such animals, the diagnosis may have to be subjected to the 

 further confirmation of a histologic examination of the 

 lesions in order to exclude tuberculosis. In cases of this 

 kind it should not be forgotten that the tubercle bacillus 

 can be present in the substances mentioned, so that the 

 exact differentiation becomes a very fine one. An instruc- 

 tive study of these organisms has been made by Abbott 

 and Gildersleeve,* who, in an elaborate work upon the 

 " Etiological Significance of the Acid-resisting Group of 

 Bacteria, and the Evidence in Favor of their Botanical 

 Relation to Bacillus Tuberculosis," a work that gives com- 

 plete references to the literature of the subject, come to the 

 following conclusions : 



1. That the majority of the acid-resisting bacteria may be dis- 

 tinguished from true tubercle bacilli by their inability to resist decolor- 

 ization by a 30 per cent, solution of nitric acid in water. 



2. That some of the acid-resisting bacteria are capable of causing 

 in rabbits and guinea-pigs nodular lesions suggestive of tubercles; 

 that these lesions, while often very much like tubercles in their histo- 

 logic structure, may nevertheless usually be distinguished from them by 

 the following peculiarities: 



(a) When occurring as a result of intravenous inoculation, they are 

 always seen in the kidneys, only occasionally in the lungs, and practi- 

 cally not at all in the other organs. 



(b) They constitute a localized lesion, having no tendency to dis- 

 semination, metastasis, or progressive destruction of tissue by casea- 

 tion. 



(c} They tend to terminate in suppuration or organization rather than 

 in progressive caseation, as is the case with true tubercles. 



(d) They are more commonly and conspicuously marked by the ac- 

 tinomyces type of development of the organisms than is the case with 

 true tubercles, and these actinomycetes are less resistant to decoloriza- 

 tion by strong acid solutions than are those occasionally seen in tubercles. 



3. That by subcutaneous, intravenous, and intrapulmonary inocula- 

 tion of hogs (4) and calves (15) the typical members of the acid-resisting 

 group are incapable of causing lesions in any way suggestive of those re- 

 sulting from similar inoculations of the same animals with true tubercle 

 bacilli. 



4. That though occasionally present in dairy products, they are to be 

 regarded as of no significance, etiologically speaking, but may be con- 

 sidered as accidental contaminations from the surroundings, and not as 

 evidence of disease in the animals. 



5. That the designation "bacillus" as applied to this group of bac- 

 teria and to the exciter of tuberculosis is a misnomer; they are more cor- 

 rectly classified as actinomyces. 



*"Univ. of Penna. Bulletin," June, 1902. 



