186 INFECTION AND IMMUNITY 



periments made with a number of microorganisms, notably the Fried- 

 lander bacillus and Staphylococcus pyogenes aureus, with dead cultures 

 of which he induced the formation of sterile abcesses in animals and 

 symptoms of toxemia. The conception of "endotoxins," subsequently, 

 however, received its clearest and most definite expression in the work 

 of Pfeiffer ^ on cholera poison. 



Some clarity of conception, based on visual perception, may possibly 

 be gained by comparing some of the products of pathogenic bacteria 

 with bacterial pigments and with insoluble interstitial or intercellular 

 substancfe, which may be seen accompanying bacteria in cover-glass 

 preparations. Soluble toxic secretions are to be compared to such pig- 

 ments as the pyocyanin of Bacillus pyocyaneus, which is so readily 

 soluble in culture media; endotoxins proper, to pigments confined to 

 the bacterial cell, or at least, when secreted, being insoluble in culture 

 media, such for instance as the well-known red pigment of Bacillus pro- 

 digiosus, which may often be seen free among the bacteria in irregular 

 red granules like carmine powder. That bodies such as this latter might 

 be extruded from pathogenic bacteria and not be soluble in the usual cul- 

 ture fluids, is not improbable, and the fact that more or less insoluble 

 interstitial substances are not infrequent among bacteria is well known. 



In all bacterial bodies, after removal of toxins and endotoxins, a 

 certain proteid residue remains which, if injected into animals, may 

 give rise to localized lesions such as abscesses or merely slight temporary 

 inflammations. The nature of this residue has been carefully studied, 

 especially by Buchner, who has named it bacterial protein and he 

 believes the substance to be approximately the same in all bacteria, 

 without specific toxic action, but with a general ability to exert a positive 

 chemotactic effect on the white blood cells, thereby causing the forma- 

 tion of pus. The nature of the bacterial proteins is by no means clear, 

 and it is still in doubt whether the separation of these substances from 

 the endotoxins can be upheld. 



A number of bacteria may give rise to both varieties of poisons. 

 Thus, recently, Kraus has claimed the discovery of a soluble toxin for 

 the cholera spirillum and Doerr for the dysentery bacillus, both of which 

 microorganisms were regarded as being purely of the endotoxin-pro- 

 ducing type. 



It is plain, moreover, that occasionally it may be very difficult to 

 distinguish between a soluble toxin and an endotoxin. In the filtration 



1 Pfeiffer, Zeit. f. Hyg., xl, 1892. 



