IMMUNITY. 2 20 



by the two schools. To the other body concerned in bacterio- 

 lysis—the amboceptor of Ehrlich and the substance sen- 

 sibilisatrice of Bordet— is assigned by the former the role of a 

 binding link between the complement and the bacterium, 

 while by the latter is assigned to it the property of a sensitizer 

 or of a mordant as in dyeing. In the one case the bacterial 

 cell is regarded as not at all injured or otherwise changed by 

 the union with the amboceptor; in the other case it is the opin- 

 ion of those holding this view that the cell is acted upon and 

 changed by the sensibilisatrice in such a way that the alexin 

 can penetrate it. 



Bordet* summarizes the difference between his theory and 

 that of Ehrlich as follows : 



According to Ehrlich and Morgenroth the specific antibody (sensibilisatrice) 

 plays the role of an actual intermediary (zwischenkorper, amboceptor), a link 

 of union attaching itself on the one hand to the cell, on the other to the alexin. 

 In other words, the absorption which the alexin undergoes in the presence of the 

 sensitized celt is not due to an affinity manifested by the cell itself to this substance 

 The absorption of the alexin is only indirect; the cell joins itself to the interme- 

 diary substance, which is itself united chemically by its other pole to the alexin. 



Our idea of the phenomenon, which we feel we are justified in holding, is alto- 

 gether different from this. To us it seems that the sensibilisatrice which unites 

 with the cell modifies this in a way which permits it to absorb the alexin directly. 

 The action of the sensibilisatrice upon the cells is comparable to that of certain 

 fixative agents or mordants which confer upon certain substances (or to the cell 

 of these substances, as is the case in histological technic) the power of absorbing 

 colors which they refuse to absorb before treatment. * * * It is to be clearly 

 understood, however, that when we speak of mordants in this connection we do 

 not intend to apply in all details the phenomena of dyeing to the matter at pres- 

 ent under consideration ; we merely mean to draw a comparison which will serve 

 to make our idea clearer. The hypothesis which we wish to bring out in relief 

 is that in the presence of hemolytic serum, the cell becomes capable of absorbing 

 directly the alexin by means of its own proper elective affinity, and that this power 

 is due to a change caused by the sensibilisatrice. In other words, we do not 

 believe that one is forced to admit, with Ehrlich and Morgenroth, that the 

 sensibilisatrice itself combines with the alexin, and that this union is indispensable 

 for the latter substance to attack the cell. 



*Bordet, Jules. Sur le mode d'action de scrums cytolytiques et sur I'unit^ 

 de I'alexine dans un meme sfrum. Ann. de I'inst. Past., T. 15, no. 5, 303-318. 

 Paris, May 25, 1901. 



