32 INFECTION AND RESISTANCE 



poisons are not true bacterial toxins, since they do not emanate 

 specifically from the cell substance of the micro-organisms but rather 

 represent incidental cleavage products of the nutrient materials. 

 Therefore, also, the ptomains are unspecific their formation a com- 

 mon attribute of a large variety of saprophytic organisms, their 

 production, as to quantity and kind, primarily dependent upon 

 the nature of the nutrient materials on which the bacteria are 

 grown. 



In contradistinction to the ptomains, the specific bacterial poi- 

 sons, in the technical meaning of the term, are substances which are 

 characteristic for each individual species of bacteria and truly the 

 products of bacterial metabolism in that they emanate from the cell 

 itself, either as a secretion or excretion during cell life, or as an 

 inherent element of the cytoplasm liberated after death (or possibly 

 as a cleavage product of the disintegrating bacterial protein). 11 

 They are dependent upon the nature of the culture medium only in 

 so far as this favors or retards the normal development of the micro- 

 organisms. While, therefore, a diphtheria bacillus undoubtedly pro- 

 duces the largest quantities of its specific poison on bouillon suitably 

 prepared for this particular purpose, it will also, in smaller amount, 

 produce qualitatively the same poison on all media on which its 

 growth is free and uninhibited, even on a medium such as that of 

 Uschinsky, which is entirely devoid of proteins. The toxins are, 

 therefore, elements of intracellul&r metabolism, permanently or 

 transiently constituent parts of the cell body. 



A specific bacterial toxin was first obtained from the diphtheria 

 bacillus by Roux and Yersin 12 in 1889. They discovered that if 

 diphtheria bacilli were grown on veal broth and the cultures filtered 

 through porcelain candles, after seven days at 37.5 C. the filtrates 

 were highly toxic, producing the same symptoms and autopsy find- 

 ings in rabbits, guinea pigs and birds which followed the injection 

 of the living bacilli themselves. The poison was therefore a soluble 

 product of the bacteria during the period of their vigorous growth, 

 apparently given up by them to the culture' fluid. Very soon after 

 this, in 1891, Kitasato 13 discovered a similar specific toxin in cul- 

 ture filtrates of the tetanus bacillus, and it was the hope of bacteri- 

 ologists that analogous poisons could be determined for all patho- 

 genic bacteria. 



This hope, however, has been disappointed. It was soon found 

 that cultures of cholera spirilla, typhoid bacilli, and many other 

 germs did not yield toxic filtrates of this kind but that the poisons 

 in these cases seemed to be firmly bound to the bacterial bodies dur- 



11 In connection with this read the discussion on anaphylaxis in chapter 

 XVII, p. 413. 



12 Roux and Yersin. Ann. de I'Inst. Pasteur, Vol. 2, 1889. 



13 Kitasato. Zeitschr. f. Hyg., 1891, Vol. 10. 



