426 PATHOGENIC MICROORGANISMS 



eighteen to twenty-four hours under partially anaerobic conditions, 

 contained definite toxic substances. Filtered through Berkefeld 

 candles and injected into rabbits in quantities ranging from 3 to 6 

 cubic centimeters, sickness consisting of general muscular weakness, 

 respiratory difficulty, and in about 8 per cent of the cases death 

 ensued. Similar toxic substances could be obtained by repeatedly 

 washing young agar growths of streptococci in salt solution and 

 filtering immediately. We do not regard these as specific exotoxins, 

 but believe them to be entirely similar to substances obtained in 

 the same way from young influenza cultures, typhoid, dysentery, 

 meningococcus and prodigiosus cultures. The work on these sub- 

 stances is not yet completed. They are not antigenic and not specific, 

 and repeated injection into rabbits in sublethal amounts produces 

 chronic emaciation and usually death after five or six injections. 

 They may well have important bearing on the symptoms of strepto- 

 coccus diseases. They are certainly neither specific exotoxins nor 

 endotoxins, and, for the present, we speak of them, for lack of a 

 better term, as "X" substances. 82 



STREPTOCOCCUS HEMOLYSIN. The production of hemolysin by 

 streptococci has been mentioned briefly in connection with our sec- 

 tion on classification, since this property has become one of the 

 important criteria of differentiation. The substance responsible for 

 the laking of red blood corpuscles, being a secretion of the organ- 

 isms, comparable to the true toxins of some other bacteria, has been 

 made the subject of a considerable number of investigations. The 

 observation of this phenomenon was first made by Marmorek 83 in 

 1895. Marmorek believed that there was a direct relation between 

 virulence and hemolytic power. Other investigators, however, 

 notably Schottmuller, 84 believed, from the beginning, that the 

 hemolytic power was a constant characteristic of certain strains, 

 unchangeable by experimental enhancement or reduction of the 

 virulence. As mentioned before, the streptococcus hemolysins may 

 be conveniently observed by cultivation of the organisms on blood 

 agar plates. The criteria for media, blood and reaction have been 

 mentioned above. The hemolysins may also be obtained in liquid 

 media by the filtration of young liquid cultures. Apparently it is 



82 Zinsser, Jour, of Immunol., 5, 1920, No. 3, p. 265 ; Zinsser, ParTcer and 

 Kuttner, Transac. Soc. Exp. Med. and Biol., Dec., 1921. 

 * 3 Marmorelc, Ann de Plnst. Past., 1895. 

 84 Schottmilllcr, Mun. med. Woch., 1903. 



