from some Old Tuherculous Lesions in Mem. 539 



were they ? Some of them undoubtedly contained acid-fast 

 bacilli. 



It may again be suggested that even the guinea-pig is not 

 entirely devoid of the power of resisting tuberculous infection, 

 and to some extent can get over small doses of bacilli, as the calf 

 and other animals, including man, undoubtedly can, and that in 

 these cases the dose was too small to infect. To this it may be 

 replied that doses apparently equally small have frequently been 

 given wath positive results, and that in some of the cases recorded, 

 notably the first, the dose cannot be considered small since many 

 thousand tubercle bacilli were present in each cubic centimetre of 

 the emulsion injected. 



I do not propose to discuss now the vitality of tubercle bacilli 

 in actively living tissues — hitherto we have been considering their 

 vitality in necrotic tissue caseous and calcareous. Many observers 

 have found living tubercle bacilli capable of infecting guinea-pigs 

 in enlarged tonsils, adenoid vegetations, or in cervical, mesenteric, 

 or bronchial lymph glands. Work of this kind carried out by 

 Weber and Baginsky for the Committee of the Gesundheitsamt, 

 however, shows that such infection is not very common. More- 

 over, as these authors remark, one cannot tell in these cases how 

 long the bacilli have been there. They might conceivably have 

 only just got into the tonsil or lymph gland in which they were 

 found. 



If it is worth while speaking at all of probabilities, it seems 

 hardly likely that bacilli could survive in living tissues which we 

 know possess some degree of bactericidal powder longer than in 

 inert, dead, caseous, or calcareous matter. 



Again it seems improbable that tubercle bacilli should remain 

 alive in a quiescent state for great lengths of time. It is generally 

 conceded that they do not form spores, and in our artificial 

 cultures their vitality is measured by months rather than by 

 years. 



Very many more observations are needed before we can form 

 any opinion as to the frequency with which living tubercle bacilli 

 are present in old and quiescent tuberculous lesions. I have 

 brought forward these few because much time must necessarily 

 pass before I can greatly enlarge the number, and because few as 

 they are they make one question, whether the frequency with 

 which old tuberculous lesions are met with in post-mortem 

 examinations really lends so much support to the hypothesis of 

 latency as it is usually held to do. 



