88 EVIDENCE IN FAVOUR OF DISSOCIATION 



would not come in. And they also showed that certain mixtures 

 of toxin and antitoxin might act fatally on rabbits in a few days 

 and cause only paralysis in guinea-pigs, but that if a little more 

 antitoxin were added it would act as a toxon on rabbits and be 

 inert to guinea-pigs. To explain this, Ehrlich had to add yet 

 another body to his list of components of the diphtheria poison, 

 and to the proto-, deutero-, trito-toxin, and toxon he added 

 toxonoid, which is inert for guinea-pigs and produces paralysis 

 in the rabbit. The subject will not be followed farther, but 

 enough has been said to show its extreme difficulty. ' 



To revert to the question of dissociation, Madsen and Walbum 

 have brought forward some definite evidence of its existence, of 

 which the more important are the following. They neutralized 

 ricin with antiricin, and to the neutral mixture added some red 

 blood-corpuscles. After allowing the mixture to stand for some 

 time, the latter were centrifugalized off, when it was found that 

 they had become charged with ricin and the fluid contained free 

 antiricin. 



Secondly, they made use of the fact that diphtheria toxin is a 

 substance of comparatively small molecule, and can diffuse 

 through gelatin, whereas its antitoxin does so very slowly. They 

 prepared a neutral mixture of the two, and placed it on the 

 surface of a column of gelatin, and after some forty days' contact 

 examined slices at different depths, and found free toxin at a 

 certain distance from the surface. This they explained by assum- 

 ing that it had dissociated from the antitoxin, and diffused down- 

 wards into the gelatin. It was pointed out, however, that if the 

 mixture had been allowed to stand for some time the phenomenon 

 did not occur ; it would seem, therefore, that the combination 

 takes place slowly, but, once formed, does not dissociate. 



There is, however, other and independent evidence in favour of 

 the theory that dissociation of a primary substance and its anti- 

 body does occur. Thus Muir and Morgenroth showed inde- 

 pendently that if red corpuscles are treated with as much 

 amboceptor as they will take up, and then mixed with normal 

 corpuscles, some of the amboceptor will pass to the latter, and 

 on the addition of a suitable complement-containing serum the 

 whole may be dissolved. (In this experiment the red corpuscles 

 correspond to the toxin, whilst the amboceptor is the antibody 

 and corresponds to the antitoxin.) 



Bordet's explanation of the phenomena is quite different. Both 



