TUBERCULOSIS. 209 



indistinct, until eventually nothing but the ghost of a cell is 

 left. This occurs where we have what is known as the 

 cheesy or caseous degeneration, in which condition nothing 

 but broken-down nuclei and very rarely a tubercle bacillus 

 can be distinguished. It would at first sight appear as 

 though the tubercle bacilli had disappeared, root and 

 branch, from this caseous centre, but if a small portion of 

 the cheesy material be inoculated into an animal susceptible 

 to tubercle, flourishing groups of tubercle nodules all con- 

 taining tubercle bacilli are produced, first near the seat of 

 inoculation, and then at points situated at some distance from 

 the point of primary infection. The results of such experi- 

 ments naturally led the opponents of the bacillary theory 

 of tubercle to assume that the poison of tubercular virus 

 was not associated with the bacillus, which they contended 

 was merely of accidental or sequential and not of causal 

 occurrence, as it could not be found in material which 

 undoubtedly produced the disease ; but after the demon- 

 stration of spores in the bacilli, and bearing in mind what was 

 known of spore formation in other organisms, most observers 

 were very naturally led to the conclusion that, although the 

 bacilli are not to be demonstrated in these infective caseous 

 masses, spores in enormous numbers are probably present, 

 and that from these, bacilli are developed as soon as the sur- 

 rounding conditions of nutrition, moisture, and heat are 

 again sufficiently favourable. The fact that it is so difiicult 

 to stain spores made it no easy task to demonstrate the 

 accuracy of this theory, but it may now be held, as the out- 

 come of inoculation and other experiments, that there can be 

 no reasonable doubt on the subject. It is a curious fact that 

 whilst in the human subject tubercle bacilli appear in many 

 cases to be actually contained within the giant or other large 

 cells, in some herbivora, and in fowls, the bacilli sometimes 

 occur single or in small masses, apparently outside the cells. 

 There are several explanations given for this, but the most 

 rational appears to be that where the bacilli are few in 

 number, and where they are being rapidly destroyed by the 

 tissue cells, by far the larger proportion are taken up by, and 

 are seen in, these cells ; this being specially observable in 

 cases of chronic tuberculosis, whilst in those cases where 

 the tubercle bacilli are relatively numerous, as in cattle, and 

 even more markedly in the fowl and in the horse, the 



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