CHAPTER XXIII. 



SPECIFIC BACTERIAL PRODUCTS, TISSUE REACTIONS 

 AND IMMUNITY. 



The first efforts in the study of the relation of bacteria to 

 animal diseases were directed to the discovery of the infecting 

 organisms. To find the specific cause and learn its life history 

 for each of the infectious and communicable diseases was the 

 task of the bacteriologist. Working with the methods intro- 

 duced by the earlier investigators the bacteria that cause a 

 number of the infectious diseases were found, isolated, and 

 carefully studied. This was closely followed and partially ac- 

 companied by a study of the products of bacterial growth and 

 their effect upon the tissues of the animal body. The re- 

 searches of Pasteur 1 in the production of immunity against 

 anthrax and chicken cholera, of Salmon and Smith 2 in the im- 

 munizing of pigeons to hog cholera, the discovery of tuber- 

 culin, diphtheria and tetanus toxins, were findings of interest 

 in the physiological properties of bacteria. These were fol- 

 lowed by a still more complicated line of investigations, 

 namely, that of the response of the body tissues to the stimulus 

 of the products of bacterial growth or toxins and the deter- 

 mination of the nature of the specific substances that are 

 given off by the tissues as a result of such stimulus. As the 

 result of this latter study we are in possession of much theo- 

 retical knowledge concerning the mechanism by which the 

 tissues of the body adjust themselves to the injuries inflicted 

 by these invading organisms or their products. The results of 

 this work have developed a large literature on the subject and 

 many new terms have been introduced to indicate the newly 

 discovered substances that have been found and the resulting 



1 Pasteur, Chamberland and Roux. Compt. rendu de 1'Acad. des 

 Sci., Vol. XCVII (1881). 



2 Salmon and Smith. Hog Cholera, B. A. I., U. S. Dept. Agric., 

 1889, p. 155. 



