298 specific Iiiflaiiu)iatio)is. 



ference between the bacilli of human and bovine tuberculosis, but 

 has met strong opposition at the hands of a large number of stu- 

 dents. In this country Ravenel and Pearson have shown distinctly 

 the identity of the microorganisms; and the work of these investi- 

 gators in inducing immunity in cattle against bovine tuberculosis 

 by vaccination with cultures of human tubercle bacilli of low viru- 

 lence is of extreme significance.] 



The variations in pathogenic power exhibited by the bacilli ob- 

 tained from different sources find their explanation in the adaptation 

 of the organisms to the different animal bodies. It is obvious and 

 reasonable that, in case of transmission of consumption which has 

 been going on for centuries from one human being to another, in 

 which the tubercle bacilli of every generation always grow ex- 

 clusively in the human body, the organisms may come to adapt 

 themselves to the conditions of nutrition which the human system 

 supplies to them, and that they attain their greatest infectious power 

 for it and find more difficulty of growth in another type of animal 

 body. In the same way tubercle bacilli which have passed through 

 many generations in the bodies of herbivora become as it were accli- 

 mated, and are best able to infect again an animal of the same species. 

 The tubercle bacilli of birds (whose normal body temperature is 

 known to be 41° -42° C, and whose tissues and fluids from their 

 known resistance to tetanus virus, etc., must have totally different 

 affinities from those of mammals) are particularly changed in their 

 biological characteristics so that thev seem to be of a totallv different 

 stock ; and, too, it is difficult to successfully induce a growth of 

 tubercle bacilli from mammals in the avian body. However, now 

 and again birds have been rendered typically tuberculous by inocu- 

 lation with mammalian tuberculosis, and conversely horses (No- 

 card) have been infected with avian tuberculosis; and therefore the 

 differences may be considered as merely expressions of a varia- 

 bility of biological properties. We must consider tuberculosis of 

 man and the animals as caused by one and the sanie infectious 

 agency, zvhich from long transmission througJi one particular animal 

 species may develop definite varieties and strains of uneven patho- 

 genic pozi'cr. (For further details consult Xocard-Leclainche : Les 

 Maladies Microbiennes des Aniinau.v. III. Ed.. Paris, 1903.) 



The anatomical lesions determined by the tubercle bacillus are 

 as follows : After being conveyed into the body of a man or ani- 

 mal the tubercle bacillus multiplies into masses, provided it finds a 

 suitable soil at the temperature of the' animal ; penetrates by growth 

 into the tissues and is carried more widely by the wandering 



