276 PUBLIC HEALTH BACTERIOLOGY 



Perchloride of mercury is not very efficient, from the 

 albuminate formed. The comparatively high powers of 

 resistance (for an organism not admitted to have spores) 

 are attributed to the protective qualities of the waxy cell 

 membrane. The conclusion then is, that moist heat at 

 100 C. will kill the bacilli in fluids and tissues, provided 

 time is given for penetration of bulky materials. In 

 Germany, tuberculous ox flesh is thus sterilized (four hours 

 boiling) and then allowed to be sold. 



Pathogenicity. For man is great : 10 per cent of all the 

 deaths in Great Britain and in the United States of America 

 are due to tuberculosis of one kind or another. This of 

 course represents only a portion of the incidence of tuber- 

 culosis, as many people are attacked and succeed in throw- 

 ing off the infection. In fact it may be said that the fatal 

 attack of tuberculosis is in many cases only the last of a 

 long series of attacks more or less successfully repulsed. 

 The commonest type in man is phthisis pulmonalis, then 

 affections of lymphatic glands, bones and joints, and serous 

 membranes. 



In America, 22 per cent of the deaths among the North 

 American Indians, and 16 per cent among the negroes, 

 are due to tuberculosis. 



For animals, the pathogenicity varies, but most are 

 vulnerable. The question is at present clouded by the 

 statement that various types of tubercle bacilli exist, 

 such as the human type, the bovine type, and the avian 

 type, and that these types vary in their power over the 

 different animal species. 



Ignoring for the moment the different types, tuberculosis 

 is mostly found in cattle and pigs. Dogs and cats 

 occasionally suffer, and monkeys and apes (immune when 

 in the wild state) are very subject to it and mostly die of 

 it in captivity. Horses are rarely attacked, and sheep 

 are practically immune. Of ah 1 the home cattle slaughtered 

 in the Glasgow market in 1910 (67,849), 12-98 per cent 

 showed lesions of tuberculosis, and of 39,724 swine, 6'I2 

 per cent ; while out of 307,784 sheep not one showed 

 tuberculous lesions. The rate among cattle is excessive 

 from the large proportion of milch cows included, some 

 of which are imported into the city and are kept in byres 



