78 BACTERIOLOGY 



their course, sometimes appearing as a row of dots. When 

 stained by the Ziehl-Neelsen carbol-fuchsin method, the 

 tubercle bacillus will withstand the action of 20 or 25 per 

 cent, sulphuric acid and of alcohol for many hours, and is the 

 most resistant member of the acid-proof group in this respect. 

 In certain tuberculous material such as old caseous glands 

 it is often difficult or impossible to demonstrate any acid- 

 proof bacilli by this method, yet such tissues, if inoculated into 

 the guinea-pig, reproduce the disease. By recent staining 

 methods such as those introduced by Professor Much (the Gram- 

 Much Method), certain more or less irregular granules may bo 

 found, and these are believed now to be a non-acid-proof and 

 still infective phase of the life-history of the organism. 

 - The bacillus was first cultivated artificially by Koch upon 

 sterilised and inspissated ox-serum. Blood-serum and various 

 egg-media, especially if smeared with a little sterile \human 

 blood, are used for obtaining primary or original cultures. 

 The suspected tuberculous material is first inoculated into a 

 guinea-pig or rabbit, or it may be treated with a powerful 

 solvent such as " antiformin," which rapidly dissolves up and 

 destroys other non-acid-proof bacteria and tissue elements, but, 

 if not too long applied, leaves the Tubercle bacillus unharmed. 

 Primary cultures are then made upon the media mentioned, 

 from the lesions resulting in the animal, or from the washed and 

 centrifugalised deposit from the antiformin-treated material. 

 The organism grows very slowly, becoming apparent usually in 

 about ten days or more, and gradually increasing for weeks 

 or months. Secondary cultures of some strains of the bacillus 

 grow well on agar and potato, and in broth, if glycerin is added 

 to them. Sterile animal tissues may also be used as a culture- 

 medium. The growth may be dry and wrinkled, or it may be 

 scaly, wax-like, or crumb-like. In such cultures, involution 

 and thread-like forms are common, and often show a marked 

 granular appearance on staining. Branching forms, suggesting 

 the possible streptothricial nature of the organism, are some- 

 times found. 



The effects of its action upon the tissues of the body are so 

 protean and complex, that special works on pathology must be 

 consulted by those who wish to understand them. It is suffi- 

 cient here to explain that the toxins of the bacillus possess the 

 power of causing the gradual or sometimes rapid death of the 

 tissues locally by a necrotic process known as cassation. The 

 tissues around the bacillus, if not too seriously damaged, are 

 stimulated to proliferate in a peculiar manner, and attempt to 

 surround and shut in the organism by a slow fibrous tissue- 

 formation around it. By a combination of these two processes 



