90 BACTERIOLOGY FOR NURSES 



lower, .134 per cent only being recorded; some 

 allowance is, however, made for the differences in 

 compiling statistics. The appearance of the tubercle 

 bacillus in man and the bovine bacillus is somewhat 

 different, the latter being shorter. The very impor- 

 tant question as to man's susceptibility to bovine 

 tuberculosis is still a matter of controversy, although 

 enough evidence has been collected to prove that the 

 bovine bacillus is found in man. Bovine infection 

 occurs much more frequently in children under 

 five years of age than in adults, which is supposed 

 to be due to their diet consisting largely of milk. 

 Tuberculous meat is less dangerous than milk, 

 because cooking will destroy the bacilli. 



Tuberculosis is common among fowls, turkeys, 

 and pigeons, but ducks and geese are exempt. Fish 

 also are affected by a disease due to an organism 

 which resembles the tubercle bacillus. 



Channels of Infection. The chief avenue of in- 

 fection is the respiratory tract. It is estimated 

 that a patient suffering from phthisis may expecto- 

 rate over 500,000,000 bacilli in twenty-four hours, 

 and even with the most scrupulous care, every act of 

 coughing or sneezing projects large numbers into the 

 air, where they may be inhaled by healthy persons. 

 The action of sunlight and of drying kills the majority 



