XON-SPORING BACILLI 289 



Three types of tubercle bacilli are described : - 



(1) Bovine tubercle bacilli the only kind found in 

 natural tuberculosis of cattle. 



(2) Human tubercle bacilli the kind most commonly 

 found in man, but not the only kind so found. 



(3) Avian tubercle bacilli the only kind found in 

 natural tuberculosis of birds. 



i- Bovine tubercle bacillus is taken as the standard 

 for comparison. 



SUMMARY OF ITS CHARACTERS. (a). Cultural. Grows 

 slowly on serum, and at the end of two to three weeks 

 shows on surface as a thin, greyish, uniform growth, not 

 wrinkled nor pigmented. According to the rate and 

 luxuriance of growth on glycerin media, bovine tubercle 

 bacilli may be divided into three grades. Nevertheless it is 

 insisted that rate and kind of growth should not be the 

 sole basis of identification as bovine type, but only when 

 considered along with results of inoculation experiments. 



(b). Effects on animals. Produces characteristic effects 

 when inoculated into calves and rabbits in certain doses. 



Calves : subcutaneous injection in neck of 50 mgr. of 

 culture under three weeks old. causes severe general 

 tuberculosis, starting at point of inoculation ; and death 

 usually within eight weeks. 



Rabbits : intravenous injection of o-oi mgr. or o-i mgr. 

 of culture causes generalized miliary tuberculosis, ending 

 in death within 5 weeks ; intraperitoneal injection of o-i 

 mgr. death in 13 to 48 days; intraperitoneal injection 

 of i-o mgr. death in 10 to 38 days; subcutaneous injection 

 of i mgr. death in 29 to 165 days; subcutaneous injection 

 of 10 mgr. death in 28 to 101 days. 



These results are very striking and definite, and along 

 with cultural tests afford a trustworthy means of recog- 

 nizing bovine tubercle bacilli. Later it was considered 

 sufficient to inoculate rabbits, as results are very reliable. 



(c). Other properties. Subcutaneous inoculation in very 

 small doses invariably produces acute tuberculosis in the 

 chimpanzee, monkey, and guinea-pig. 



In the goat, the pig, and the cat, general tuberculosis 

 is readily induced. 



The rat and the mouse are highly resistant to sub- 



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