134 PROTEIN POISONS 



immediate cause of death is asphyxia brought about by 

 paralysis of respiration through the action of the poison. 1 



This action of the heart after the cessation of respiration 

 is exceedingly interesting, and is entirely analogous to that 

 mentioned as following the intraperitoneal injection. The 

 rate of the beat is decidedly lessened and at first the indi- 

 vidual beats are stronger. They gradually become more 

 and more feeble, however, until finally the heart stops in 

 diastole, the rate after the preliminary slowing remaining 

 unchanged until the end. It is worthy of note that in the 

 case of intravenous injections the fall of temperature, which 

 is so marked a feature after the intraperitoneal and 

 subcutaneous injections of the poison does not occur. 

 The explanation of this fact is doubtless to be found in the 

 very short interval of time which elapses between the 

 injection and a fatal outcome. As regards the size of the 

 lethal dose when given intravenously, we see that 10 mg. 

 often, and 15 mg. invariably, proved fatal. 2 



For purposes of comparison, we have always made use 

 of the poison obtained from the same extraction in our 

 intravenous, subcutaneous, and intraperitoneal injections, 

 and have therefore been able to ascertain with a fair degree 

 of accuracy the differences in dose required to bring about 

 a fatal result in the three cases. Thus, whereas 60 mg. 

 represents the fatal dose when given intraperitoneally, it 

 requires between 120 and 180 mgs. subcutaneously, and 

 only from 10 to 15 mgs. of the same poison to cause death 

 when given intravenously. These differences are un- 

 doubtedly due to the rapidity of absorption in the various 

 cases, and a fatal issue depends entirely on whether suffi- 

 cient poison reaches the sensitive area at one time to cause 

 cessation of respiration or not. 



It has now been shown that a very powerful intracellular 

 poison can be obtained from the colon bacillus. As has 

 been previously stated, the results given in the foregoing 

 experiments are those obtained with the poison from one 



1 The physiological action of this protein poison is discussed on page 315. 



2 The fatal dose of the purest form of the poison which we have 

 obtained is 0.5 mg. intracardially. 



