424 MYCOBACTERIUM 



most extensive in the lungs and spleen, and less extensive in the liver and kidneys. Smaller 

 doses give less constant results. The intravenous injection of even 1 mgm. of bovine bacilli 

 produces a severe and fatal tuberculosis. Cattle may likewise be infected with bovine 

 bacilli by inhalation and feeding. 



The subcutaneous injection of calves with human bacilli, in no matter what dosage, 

 never gives rise to a progressive disease. At most there is a local abscess and swelling 

 of the focal glands ; when the animals are killed after 4 or 5 months, the lesions are minimal, 

 and are often calcified. The intravenous injection of human bacilli may cause death by 

 toxjemia with acute infiltration and oedema of the lungs ; but there is no true infection. 

 The same toxaemia may be produced by the intravenous injection of avian bacilli, and 

 even of the non-pathogenic saprophytic acid-fast bacilli. 



The intramuscular inoculation of a calf with 80 mgm. of murine bacilli gave rise to 

 a local abscess and to inconspicuous lesions in the regional lymphatic glands. Even 

 10 mgm. intravenously excited no more than a mild chronic retrogressive tuberculous 

 reaction (Griffith and Bailing 1940). 



The subcutaneous injection of calves with avian bacilli in a dose of 500 mgm. produces 

 no more than a local lesion, with perhaps a caseous nodule in the nearest lymphatic gland. 

 Intravenous inoculation, however, of even 5 mgm. may prove fatal in 2 to 3 weeks. Post 

 mortem there are miliary tubercles in the lungs ; the spleen, though showing no macroscopic 

 tubercles, is enlarged and contains great numbers of tubercle bacilli visible microscopically. 



Goats. — Bovine bacilli inoculated subcutaneously in a dose of 1 mgm. give rise to a 

 fatal, generalized disease. Human bacUli, even in a dose of 100 mgm., cause no more than 

 small retrogressive lesions. Avian bacUli in a dose of 100 mgm. rarely give rise to pro- 

 gressive disease ; on the other hand the animals may remain chronically infected and 

 excrete the bacilli in the milk for a long time (Griffith 1931). 



Sheep resemble goats in being highly susceptible to infection with bovine bacilli, 

 moderately susceptible to infection with avian bacilli, and resistant to infection with 

 human bacilli. 



Pigs. — Injected subcutaneously, the bovine type in a dose of 10 to 50 mgm. produces 

 rapidly fatal miliary tuberculosis. The human type in a dose of 50 mgm. produces a local 

 lesion with slight dissemination. Avian bacilli injected subcutaneously do not give rise 

 to progressive disease, but they may multiply and be disseminated through the internal 

 organs, where they remain alive for some considerable time. Young pigs fed with bovine 

 bacilli develop widespread disease and generally die ; when fed with human bacilli they 

 may develop extensive glandular and pulmonary disease. Though the human bacilli cause 

 less severe and less extensive tuberculosis than bacilli of the bovine type, they are more 

 pathogenic for pigs than they are for cattle. 



Rabbits. — Bovine bacilli injected subcutaneously in a dose of 0- 1-1-0 mgm. produce 

 a generalized disease, fatal in 2 to 3 months. At necropsy a local caseous lesion, caseous 

 focal glands, innumerable little grey tubercles with caseating centres or larger irregular 

 nodules in the lungs, numerous projecting hemispherical nodules in the cortex of the 

 kidneys, and tubercles in the spleen and liver are found. Given intraperitoneally, even 

 minute doses, such as 0-000,000,001 mgm. of bovine bacilli, are said to prove fatal in 2 to 3 

 months (Cobbett 1917). Intravenous injection of 0-01-0-1 mgm. of bovine baciUi proves 

 fatal in 3 to 6 weeks. 



The subcutaneous injection oi human bacilli in a dose of 1-100 mgm. never causes fatal 

 tuberculosis. Human bacilli may, however, give rise to lesions in the lungs and kidneys. 

 Usually the lungs contain a few small grey tubercles or caseous nodules, and the kidneys 

 show a few miliary tubercles in the cortex. But th3 acute fatal miliary tuberculosis seen 

 after injection of bovine bacilli never results from the subcutaneous injection of human 

 bacilli. Intravenous and intraperitoneal injections are less reliable for purposes of dif- 

 ferentiation ; 0-01 mgm. of human bacilli given intravenously rarely, if ever, proves fatal, 

 but larger doses may give rise to a progressive fatal disease. Doses of 10-50 mgm. given 



