20 IMMUNE SERA 



tive serum shows that no separation of the several 

 antibodies developed in an individual serum is 

 possible. In the case of antitoxic sera both Gibson 

 and Ledingham find that in goat serum the antitoxin 

 is not invariably associated with the euglobulin 

 fraction as maintained by Pick, but shows the same 

 solubilities as that in horse serum. 



Toxins and other Poisonous Cell Derivatives, in 

 General. Soon after bacteriology had demon- 

 strated the etiological connection between bacteria 

 and disease, the conviction gained ground that it 

 was less the actual destruction wrought by the 

 bacteria directly, than the injury produced by their 

 chemical products that gave rise to the lesions in 

 the infectious diseases. Brieger, especially, was 

 one of the first to direct attention to the probable 

 existence of specific poisons in the bacteria. He 

 isolated a number of well defined chemical sub- 

 stances called ptomaines, most of which were highly 

 toxic. Subsequent study, however, showed that 

 these were not the specific bacterial poisons. The 

 latter, the true toxins are something quite different 

 as we shall see in a moment. Still later other 

 substances were isolated from bacteria, and these 

 were termed toxalbumins. We now know that 

 some of these were identical with the true toxins, 

 but that others were entirely unrelated. 



What then are the true toxins? A number of 

 pathogenic bacteria, when grown in pure culture, 



