SUBSTANXES PRODUCED IN BACTERIAL CULTURES. 5 1 



II. 



A very important consideration is whether these substances 

 represent toxic split products of the culture fluids produced by the 

 bacterial growth, rather than toxic products secreted by the bac- 

 teria. In favor of regarding them as split products of the medium 

 is the fact that they were more potent when the media was rich 

 in proteins. Also suggesting this is their apparent non-specificity, 

 in that, as will be shown directly, we obtained similar substances 

 from many other organisms including non-pathogens. Again, in 

 our experiments up to date, as will be seen, we have no reason to 

 believe that they are in any sense antigenic. 



Against the conception that they are split products of the con- 

 stituents of the media are the following facts: 



The substances were often high in potency from simple hormone 

 media, as well as from media containing rabbit's blood and other 

 proteins. 



It seems that they are more potent in young cultures at the 

 height of their growth energy. Potency seems to be at its maxi- 

 mum after 22 hours, decreasing with 48 and 72 hour incubation 

 periods. 



There is definite diminution of potency by filtration. 

 That there is a definite loss of potency by heating it 8o° or 

 below. 



That there is a definite incubation time, rarely shorter than 

 one hour, and never shorter than 40 minutes, even when large 

 doses of relatively high potency are injected. 



The incubation period which is characteristic of these "X" 

 substances, differentiates them sharply from histamin and tyra- 

 min. Furthermore, the symptoms produced in rabbits by injec- 

 tions of ergamine differed distinctly from the symptoms produced 

 by the "X" substances. The histamin when injected into rabbits 

 in minimum lethal doses produced immediate acute death, and 

 when injected in sublethal doses produced immediate sickness, 

 followed by recovery, the animal usually being perfectly well after 

 J/2 hour. The supposition that the toxic action of the "X" sub- 

 stances might be due to substances analogous to histamin produced 

 by the growth of the bacteria in the culture media, is thus rendered 

 unlikely since the symptoms produced by the latter class of sub- 



