14 A. L. PlERSTORFF 



any other culture, and it also gave a fairly high percentage of infec- 

 tions; but after infection had taken place, it progressed more slowly 

 and ceased invasions of new tissues earlier than did cultures T, F, D, or S. 

 Culture A was used as a standard for these tests as well as for the 

 work on enzymes and toxins. In not one of the tests made on five dif- 

 ferent dates did this culture exceed T, S, or Ti in number of infections 

 or in average of total length of twig killed. Further work is needed 

 to compare the same cultures in a larger number of experiments. 



PRODUCTION OP TOXINS 



That true bacterial toxins (exotoxins) are formed by Corynebac- 

 teriwm diphtheriae (Klebs-Lomer) Lehman and Neuman, Clostridium 

 tetani (Nicolaier) Holland, C. botulinum (Van Ermengem) Holland, 

 and Pseudomonas aeruginosa (Schroter) Migula, is common knowledge 

 among bacteriologists. Antitoxins (the production of which is one of 

 the tests for a true toxin in animal pathology) can be prepared for 

 the organism mentioned. Other groups of bacteria, such as the staphy- 

 lococci, the streptococci, and the pneumococci, produce endotoxins, which 

 are preformed toxic substances retained in the bodies of the micropara- 

 sites until released by disintegrative processes. Satisfactory antitoxins 

 have not been prepared for these endotoxins. 



Some plant pathologists are of the opinion that bacterial phytopatho- 

 genes form toxins under certain conditions, but relatively little study 

 has been devoted to this phase of the subject. 



Shortly after the discovery of the causal organism of fire blight by 

 P. or rill (1878, 1879), various workers sought to demonstrate a toxic or 

 an enzymic substance produced by Bacillus amylovorus as a possible 

 explanation of the killing power of this pathogene. Arthur (1886), 

 with the assistance of a chemist, performed repeated tests for " pto- 

 maines. " They concluded that no ptomaines were produced. The 

 methods employed at that early date would probably have destroyed 

 any enzyme or organic toxins produced by the organism. D. H. Jones 

 (1909) made exhaustive cultural studies of the organism, but found no 

 toxin produced in culture. Bachmann (1913) finds that "all of the first 

 changes in the cells which result from infection may be attributed 

 wholly to a loss of water." Stewart (1913 : 360) heartily disagrees with 

 Bachmann, and points out that if plasmolysis of the host cells is due 

 to water loss, an equilibrium in osmotic pressure should soon be estab- 

 lished, the cells should regain their turgidity, and no further killing 

 would ensue. He thought that a toxic or an enzymic substance caused 

 the killing of the host cells, but failed to find such a substance in bouillon 

 cultures. In studying the formation of schizogenous cavities, Nixon 



