126 INFECTION 



Anti-aggressins may be produced experimentally by gradually 

 immunizing animals with sterile exudates, and this immunity may be 

 transferred passively from one animal to the other by inoculation of its 

 immune serum. These anti-aggressins are quite specific, and neutralize 

 the aggressins in an exudate. 



BACTERIAL PROTEINS 



In practically all bacterial bodies, after removal of toxins and endo- 

 toxins, a certain proteid residue remains, which, when injected into 

 animals, is able to produce various grades of inflammatory reaction 

 leading to tissue necrosis and abscess formation. This substance was 

 first thoroughly studied by Buchner, who named it bacterial protein, and 

 regarded it as identical in all bacteria, and having no specific toxic action, 

 but characterized in general by its power of exerting a positive chemo- 

 tactic influence on leukocytes, and thereby favoring the formation of pus. 

 For example, in the development of an ordinary staphylococcus abscess 

 it is probable that the proteins of the cocci, aside from their toxins, aid 

 in producing tissue necrosis and in attracting leukocytes to the infected 

 area. Similarly, an extract of dead tubercle bacilli may produce a 

 tuberculoma or the tissue changes incident to tuberculosis, differing, 

 however, from true tubercle in that they do not contain living bacilli 

 and consequently are not infectious. When cultures of diphtheria 

 bacilli are filtered and the residue washed, it is found that extracts of the 

 bacterial substances or the bodies of the dead bacilli themselves are quite 

 free from the typical toxin; but the bacterial substances or the proteins 

 isolated from them, when injected into the subcutaneous tissues of 

 animals, are found to produce a strong inflammatory reaction and necro- 

 sis of the tissue-cells. 



Bacterial Split Proteins. These have been studied extensively by 

 Vaughan and his coworkers, who have ascribed to them the chief role 

 in and a very important relation to the processes of infection and im- 

 munity. 



Massive cultures of colon, typhoid, pneumonia, and diphtheria microorganisms 

 are grown in special large tanks containing agar; anthrax is grown in Roux flasks, 

 and tubercle bacilli in glycerin beef -tea cultures. After removal of the growths the 

 bacterial cellular substances are washed once or twice with sterile salt solution by 

 decantation, and then repeatedly washed with alcohol, beginning with 50 per cent, 

 and increasing the strength to 95 per cent. The substance is then placed in large 

 Soxhelet's flasks and extracted first for one or two days with absolute alcohol, and 

 then for three or four days with ether. These extractions should be thorough in 

 order to remove all traces of fats and waxes. 



