456 THE TUBERCLE BACILLUS GROUP 



Feces. Tubercle bacilli may appear in the feces either because they 

 have been swallowed with the sputum or because of the existence of 

 tuberculous ulcers in the intestinal tract. 1 Acid-fast bacilli which are 

 not true tubercle bacilli are quite common in the feces, and for this 

 reason animal inoculation after treatment of the feces with antifonnin 

 is the best method for demonstrating the organism. 



Milk. Tubercle bacilli are very infrequent in human milk, although 

 they are said to be relatively common in unpasteurized cow's milk 

 as it is sold in large cities. The organisms get into the cow's milk far 

 more frequently through the contamination with feces than from 

 direct infection through the udder. Microscopical examination of 

 the sediment of milk or cream is usually valueless, as is the examina- 

 tion of the cream layer itself. Acid-fast bacilli which are not tubercle 

 bacilli very frequently cause confusion. Among these organisms are 

 those described by Petri and Rabinovitch, which are called butter 

 bacilli. Inoculation of the sediment and of the cream of milk into 

 guinea-pigs is the only safe test. 



Immunity and Immunization. 2 The disproportion between the inci- 

 dence of "healed tubercles" in cadavers which do not exhibit symptoms 

 of tuberculosis ante mortem and the actual number of clinical cases 

 suggests that the average individual possesses a certain degree of 

 refractoriness to progressive invasion by the tubercle bacillus, that 

 is to say, the clinical cases of the disease are considerably outnumbered 

 by those in whom the organism has gained entrance, but failed to 

 develop sufficiently to cause symptoms. Early, uncomplicated cases 

 of tuberculosis frequently react favorably when placed in a favorable 

 environment. Spontaneous recovery from tuberculosis complicated 

 by secondary infections with other bacteria is more tedious and the 

 prognosis is generally less favorable. 



Active immunization of man with various products of the tubercle 

 bacillus has been one of the greatest problems of medicine. Up to 

 the present time the solution of this problem has not been realized. 

 At least a generation must elapse before final judgment can be passed 

 upon any system of human immunization, for the disease tuberculosis 

 progresses slowly and results to be trustworthy must be numerous and 

 of long duration. 



1 Laird, Kite, and Stewart, Jour. Med. Research, 1913, x'xix, 31, for summary and 

 literature. 



2 For an excellent summary of Immunity in Tuberculosis, see Baldwin, Am. Jour. Med. 

 Sc., 1915, cxlix, 822. 



