CHOLERA VIRUS. 151 



points in connection with these plasmines are that they are only very 

 slightly poisonous, and that the immunity that they confer is apparently 

 a true bactericidal one ; it is not as yet possible to prove that the active 

 substances expressed are those that cause the formation of the bactericidal 

 intermediate products. This question is of great theoretical importance 

 and will be specially dealt with when we come to consider Tuberculine 

 (q.v.). Buchner's plasmines cannot help us in the matter of the poisons 

 and antitoxines of cholera. 



It is not altogether easy to form a definite conception of the 

 nature and mode of action of cholera virus from these apparently 

 contradictory experimental results. 



For this purpose the question must be formulated in a more 

 precise manner in accordance with our theoretical conceptions 

 concerning bacterial toxines. 



The question is then no longer: " Do the vibriones produce 

 a soluble poison that gives rise to choleraic symptoms'?" but 

 it is necessary to ask whether they produce a toxine i.e., a 

 poison which enters into combination in a specific manner, and 

 eventually produces specific antitoxic immunity. 



When we put the question in this form the following conclu- 

 sions may apparently be drawn with some degree of probability 

 from the experimental results. 



It appears to be the fact that the vibriones produce a true 

 toxine, which is very sensitive to all external influences, and 

 even through the ageing of the cultivations undergoes a change 

 in a manner that has yet to be further investigated. This toxine 

 differs materially, however, from those of the diphtheria type, in 

 that it is not, like such toxines, secreted in the free state and 

 almost without residue by the vibriones, but appears to be 

 energetically retained by them intra vitam. We here meet with 

 peculiarities similar to those that occur in the case of true 

 ferments. While, for example, yeast excretes only one enzyme, 

 yeast diastase, it also contains others e.g.,invertase and maltase 

 which are not given up by the living yeast cell, and can only be 

 extracted after the cell has been killed, or after its membrane 

 has been ruptured by means of glass powder. 



In addition fco these the yeast cell also contains E. Buchner's 

 zymase, which can only be set at liberty by the very drastic 

 means of trituration and expression under high pressure. 



Perfectly analogous conditions are found in the case of the 

 inverting enzyme of Monilia Candida, which is also active after 

 the addition of toluene, but has not yet been isolated from the 

 cell of the mould-fungus by any of these methods. 1 



1 For further details of these ' ' Endoenzymes " see my Ferments and 

 their Actions, Griffin & Co., London. 



