536 Dr Cobbett, The Absence of Living Tubercle Bacilli 



The Absence of Living Tubercle Bacilli from some Old Tuber- 

 culous Lesions in Man. By Louis Cobbett, M.D. Pathological 

 Laboratory. 



[Bead 6 June 1910.] 



Two theories of the origin of phthisis involve the hypothesis 

 of latency — Baumgarten's which regards infection as occurring 

 before birth, and remaining undeveloped, perhaps for years ; and 

 Behring's which regards infection as occurring usually during 

 infancy, and remaining latent until some disturbance of health 

 set up by the onset of puberty, by parturition or lactation, or by 

 measles or some other of the specific fevers or some other cause 

 weakens the natural powers of resistance and so favours the 

 growth of the bacilli. " Then," to translate Behring's words, " we 

 have the beginning of phthisis, but the real origin of the tuber- 

 culous infection is far back." Both theories then assume that the 

 tubercle bacillus is capable of remaining alive quiescent in animal 

 tissues for long periods of time, measured not by weeks and months 

 but by years. 



Behring in arriving at his views was largely influenced by the 

 frequency with which lesions apparently tuberculous are found, 

 often quite unexpectedly, in the bodies of those who die from all 

 sorts of causes. 



These lesions undoubtedly occur very frequently, though 

 opinions may differ as to just how common they are. The 

 difference of opinion is due to the difficulty of deciding in some 

 cases whether the lesion is tuberculous or not. But in many cases 

 there is no difficulty at all, there is definite caseation or calcifica- 

 tion, and in some the characteristically acid-fast tubercle bacilli 

 may even be seen under the microscope. In such cases very little 

 attention seems to have been paid to the question whether the 

 lesion was really quiescent, or healed, that is to say whether it 

 did or did not contain living bacilli capable under favourable 

 conditions of causing a tuberculous infection. 



During the time when I was working for the Royal Com- 

 mission on Tuberculosis I was more than once astonished to find 

 that what I regarded as undoubtedly tuberculous material had 

 no effect when injected into the guinea-pig ; and, as this is one of 

 the most sensitive of animals to tuberculosis, whether caused by 

 bacilli of the human or bovine variety, I could not but regard 

 the lesions from which this material had come as cured, that is to 

 say incapable of giving rise to any further tuberculous trouble. 



Since I left Stansted I have continued to investigate isolated 

 and unsuspected tuberculous lesions, which have been from time to 



