224 TUBERCULOSIS. 



this means to inhalations for half an hour on three successive 

 days, and were afterwards kept in healthy conditions. 

 Some of the rabbits and guinea-pigs died within four weeks, 

 the others were killed at the end of that time, and all 

 showed tubercular lesions in the lungs which, in the case of 

 the rabbits and the guinea-pigs, were in the form of patches 

 of caseating catarrhal pneumonia. 



To obtain pure cultures of the tubercle bacilli, the acute 

 lesions in the organs of an animal recently killed should be 

 selected, e.g., the spleen of a guinea-pig with early acute tuber- 

 culosis. If the lesions are subacute or chronic with much 

 caseation, attempts at cultivation often fail. It would 

 appear as if a considerable number of bacilli required to be 

 present to start the growth. The portions of tissue must, 

 of course, be taken with aseptic precautions, the knives, 

 scissors, etc., to be used being carefully sterilised, and the 

 inoculations should be made on solidified blood serum. 



Avian Tuberculosis. There can be no doubt that the 

 bacilli present in tuberculosis of the various mammals 

 mentioned are of the same variety, though differences in 

 virulence may be occasionally noticed. There has, how- 

 ever, of late years been considerable discussion as regards 

 the identity of the bacilli in avian and mammalian tuber- 

 culosis. In the tubercular lesions in birds there are found 

 bacilli which correspond in their staining reactions and in 

 their morphological characters with those in mammals, but 

 differences are observed in cultures, and also on experi- 

 mental inoculation. Koch, at the International Medical 

 Congress in 1890, related how he had received from other 

 observers some cultures of tubercle bacilli which showed 

 differences in culture, and which led, on experimental inocu- 

 lation, to conflicting results. He made various attempts, 

 by altering the conditions of growth, etc., to modify these 

 cultures so as to make them conform to ordinary tubercle 

 bacilli, but failed. Later, by accident, he found, on cultiva- 

 ting the bacilli from tuberculosis of fowls, that the cultures 

 obtained corresponded with those which showed the 

 peculiarities referred to. He thus found that important 



