GENUS BACTERIUM 259 



individual, that is, a general effect. Third, a hyperemia of the 

 tuberculous focus. These can be demonstrated in the tuber- 

 culous guinea pig. The extent of the hyperemia of the tuber- 

 culous focus in cattle does not seem to be as marked as in the 

 guinea pig ; but the explanation for the rise of temperature in 

 the tuberculous body following the injection of tuberculin has 

 not been so easy to determine. A number of explanations for 

 the action of tuberculin have been offered, 30 but the one first 

 suggested by Eber 31 and more recently modified by Theobald 

 Smith 32 seems to meet the conditions better than any of the 

 others. It is as follows : 



"In the tubercular tissue and its immediate vicinity the 

 tubercle bacilli have induced certain tissue changes, and with 

 them certain new functions of the tissue have been aroused, 

 which are the result of immunization. These new properties 

 are concentrated in the immediate neighborhood of the focus. 

 The specific resistance is, as it were, chiefly focal and only 

 secondarily generalized. When the tuberculin comes in con- 

 tact with this focus, the former is acted on, with the result that 

 the originally inocuous tuberculin becomes poisonous perhaps 

 by the splitting off of some poisonous substance. An incom- 

 plete digestion I should prefer to call it. As a result of this 

 action we have, first, the local hyperemia and, second, the con- 

 stitutional effect. In other words, the tuberculin becomes 

 poisonous by an immune reaction directed toward the tubercle 

 bacillus. This reaction is defective and in so far dangerous to 

 the host. The only way in which the danger can be met is for 

 the body to produce an antibody to this second substance. So 

 far there is little evidence to show that the body is able to 

 produce this in any amount, The animal body has learned to 



30 Citron. (Berliner klin. Wochenschrift, 1907) expresses the 

 opinion that the reaction to tuberculin consists in the multiplication 

 of sessile cell receptors and free antibodies at the focus of infection, 

 after which the latter disappear. He states further that in the last 

 stage of the reaction there are numerous fixed cell receptors and 

 free antibodies in the tuberculous foci and in the serum. 



- 1 Eber. Deutsche Zeitschrift fur Tiermedizin, Vol. 21, p. 34. 



:B Smith. The Harvey Lectures, 1905-6, p. 272. 



