BACTERIA AND DISEASE 279 



genie microbes which can live and thrive independent of a 

 living host. ' ' 



It has now been abundantly proved that the bacillus of 

 tuberculosis is capable of accommodating itself to circum- 

 stances much less favourable than had been supposed, 

 especially as regards temperature. 



Temperature of Growth of Bacillus. 30-41 C. have been 

 laid down by Koch as the limits of temperature at which the 

 bacillus will grow in culture medium outside the body. The 

 generally accepted temperatures as most favourable to 

 the growth of the bacillus are between 36 C. and 38 C. 



Sir Hugh Beevor, however, was able to grow the bacillus 

 upon glycerine agar at 28 C. (82 F.), obtaining an ample 

 culture which developed somewhat more slowly than on 

 blood serum, and to a less extent than at 37 C. In both 

 Beevor succeeded in growing the bacillus at a lower temper- 

 ature even than on agar, viz., at a temperature rarely above 

 60 F. Sheridan Delepine and others have also been suc- 

 cessful in obtaining growths at room temperature both in 

 summer and winter. 



Although, speaking generally, there is an actual cessation 

 of growth at low temperature, the bacillus may be exposed 

 to very low temperatures for a considerable time without 

 losing its power of again becoming active when returned to 

 a favourable environment (Woodhead). 



The Relation of the Bacillus to the Disease. All four of 

 Koch's postulates have been fulfilled in the case of Bacillus 

 tuberculosis. Hence we are dealing with the specific cause 

 of the disease. Yet, whilst this is so, we may usefully ask 

 ourselves: How does the bacillus set up the changes in 

 normal tissues which result in tubercular nodules ? In 

 arriving at a solution of this problem we are materially aided 

 if we bear in mind the fact that such an organism in healthy 

 tissues has a double effect. First, there is an ordinary in- 

 flammatory irritation, and secondly, there is a specific change 



