140 Society for Experimental Biology and Medicine. 



with an intravenous injection, the time may be even shorter than 

 this. The fatal dose may vary from eight to one hundred milli- 

 grams according to the purity of the poison or the mode of 

 administration. While the fatal dose may be small the range 

 between that necessary to induce the first and second stages and 

 that necessary to kill may be wide. With one preparation seventy 

 milligrams was required to kill, but five milligrams developed the 

 first and second stages in pronounced forms. 



Death is due to failure of respiration and the heart often con- 

 tinues to beat for some minutes after respiration has ceased. It 

 seems most probable that death is due to the direct action of the 

 poisons on the respiratory center. It is inferred from the readi- 

 ness with which recovery may follow non-fatal doses that the poison 

 cripples but does not destroy the cells of the respiratory center. 



All attempts to produce antitoxins with these proteid poisons 

 have, so far, failed. It is true that repeated treatments of animals 

 with non-fatal doses of the poisons from the colon and typhoid 

 bacilli enable animals to bear from two to four times the ordinarily 

 fatal doses of living cultures of these bacteria, but this seems to be 

 due to an increased resistance rather than to a true immunity. 

 This condition is not specific and may be induced by the poisons 

 obtained from peptone or egg white, as well as with that obtained 

 by cleavage of the homologous bacterium. 



Attempts have been made to ascertain the chemical constitu- 

 tion of the proteid poisons by splitting them up with mineral acids 

 but at present these experiments have not yielded satisfactory 

 knowledge and work along this line is being continued. The 

 physiologic action of the proteid poisons leads to the suspicion 

 that they contain a neurin group, but so far we have not been able 

 to demonstrate the presence of such a body. 



98 (241) 



Observations on the living developing nerve fiber. 

 By ROSS G. HARRISON. 



[From the Anatomical Laboratory of the Johns Hopkins University.] 



The immediate object of the following experiments was to 

 obtain a method by which the end of a growing nerve could be 



