THE BACILLUS AND THE BACTERIOLOGY OF DIPHTHERIA 213 



Toxon. This he now designates as toxon in order to distinguish it 

 from that other constituent of diphtheria bouillon, the toxin, which 

 causes the acute phenomena of diphtheria. 



Let one now add still smaller amounts of the antitoxin unit to the 

 200 binding units of the toxin. When 149/200 are added it is found that 

 a certain amount of true toxin remains free, and, moreover, is free in 

 direct proportion to the amount of antitoxin withheld. Consequently 

 when but 50/200 antitoxin unit is added the amount of free toxin corre- 

 sponds to 100 binding units. If true toxin only remained a continua- 

 tion of the experiment would show toxin equals 150. It could then be 

 said that the constitution of this toxin is : toxin 150 and toxon 50. How- 

 ever, it may be found that as 49/200, 48/200, etc., to 0/200 antitoxin 

 unit are added, no increase of free toxin is found, although the antitoxin 

 added has been found. Therefore, the 50 toxin binding units which 

 have the greatest affinity for antitoxin are non-toxic i. e., they are 

 toxoids, and since they have the maximum affinity for antitoxin they 

 are called protoxoids. 



It has been assumed also that a toxoid may exist which has an affinity 

 for antitoxin exactly equalling that which toxin possesses; this as yet 

 purely hypothetical constituent bears the name of syntoxoid. 



Refinements in experimentation show that even the true toxin is not 

 uniform in its virulence and its affinity for antitoxin. Accordingly, a 

 prototoxin, a deuterotoxin, and a tritotoxin may be recognized by this 

 same partial saturation method. For example, it may be found that 

 when a portion of the antitoxin unit, between the limits of 149/200 and 

 125 200, is withheld, a toxin is left free w r hich is less virulent than that 

 remaining free between the limits of 124/200 and 100/200; and from this 

 point on the new unbound toxin may be still more virulent. The first 

 would be tritotoxin, the second deuterotoxin, and the third prototoxin. 



A "spectrum" having been \vorked out for a toxin when fresh, an 

 examination made some time later, a year for example, may show many 

 changes. The prototoxin zone and portions of the deuterotoxin or 

 tritotoxin may also have disappeared because of toxoid formation. 

 These changes have led to the recognition of an alpha and a beta 

 modification of the toxin portions. The alpha modifications of all 

 three toxins readily become toxoids. Only the beta modification of 

 the deuterotoxin remains constant. The toxon portion also remains 

 relatively intact. 



Summary. To summarize Ehrlich's views as to the nature of diph- 

 theria toxin : The diphtheria bacillus secretes two toxins, one of which, 

 the toxin, causes the acute phenomena of diphtheria intoxication, while 

 the other, the toxon, causes cachexia and paralysis after a rather long 

 period of incubation. The non-toxic toxin, or toxoid, appears as the 

 result of the degeneration of the toxophore group of the toxin, the 

 haptophore group remaining intact. The toxin may be separated into 

 three divisions, which vary in their affinity for antitoxin prototoxin, 

 deuterotoxin, and tritotoxin. On the same basis there are three toxoids 

 protoxoids, syntoxoids, and epi toxoid (the toxon) the first having 



