KOCH'S TUBERCLE BACILLUS 329 



Spore formation. — In very old cultivations spore-like bodies can 

 be observed both in stained and unstained. preparations, but neither 

 the irregular granules within the capsule nor the unstained spaces 

 between the granules are spores (Babes and Crookshank). That the 

 bacilli probably possess spores is believed on account of their 

 behaviour under certain circumstances. For example, tubercular 

 sputum when thoroughly dried retains its virulent character. Even 

 cultures of tubercle artificially dried retain their virulence. Now, 

 no sporeless bacillus is known at present which can withstand thorough 

 desiccation. Again, non-spore-bearing bacilli are killed with a less 

 exposure to heat than that which is required to destroy tubercular 

 sputum. Koch, Lingard, Klein, and others long ago pointed out the 

 resistance of the bacilli of tubercle to solutions of perchloride of mercury 

 and to heating in suspension in salt solution, whilst sporeless bacilli 

 succumbed to the same treatment. So that it is commonly believed 

 that B. tuberculosis produces spores, even though such have not been 

 demonstrably proved. 



Koch and other bacteriologists have declared the bacillus to be 

 a " true parasite." Koch based this view upon the belief which he 

 entertained that the bacillus can only grow between 30° C. and 

 41° C, and therefore in temperate zones is limited to the animal 

 body, and can only originate in an animal organism. " They are," 

 he said, "true parasites, which cannot live without their hosts. 

 They pass through the whole cycle of their existence in the body." 

 But at length Koch and others overcame the difficulties and grew 

 the bacillus as a saprophyte. Schottelius* has observed that 

 tubercle bacilK taken from the lung of phthisical persons buried for 

 years still retains its virulence and capability of producing tuber- 

 culosis upon inoculation. He further showed that tubercular lung 

 kept in soil (enclosed in a box) revealed a marked rise in temperature. 

 Klein quotes these experiments as indications that " tubercle bacilli 

 are not true parasites, but belong to the ectogenic microbes which 

 can live and thrive independently of a living host." 



It has now been abundantly proved that the tubercle bacillus 

 is capable of accommodating itself to circumstances much less 

 favourable than had been supposed, as regards temperature and 

 environment. For it is now known that it is possible to grow the 

 baciUus upon glycerine agar at 28° 0. (82° F.), obtaining an ample 

 culture which develops somewhat more slowly than on blood serum, 

 and to a less extent than at 37° 0. Sheridan, Del(5pine, Czaplewski, 

 Kansome, Beevor, and others have also been successful in obtaining 

 growths at room temperature both in summer and winter. Moeller 

 succeeded in growing the bacillus at 20° C, after passing it through 

 a blindworm. 



* Gentralblatt. f. Bad. und Parasit. , vol. vii. , p. 9. 



