NATURE OF ANTITOXIC ACTION. 475 



These investigations are specially instructive, as the 

 poisons, both as regards their local action and the general 

 toxic phenomena produced by them, present, as we have 

 seen, an analogy to various toxines of bacteria. 



Nature of Antitoxic Action. On this subject there has 

 been much diversity of opinion. Some observers consider 

 that the antagonism between toxine and antitoxine depends 

 upon a chemical union between the two substances, whilst 

 others consider that it is of a physiological nature, the anti- 

 toxine acting through the medium of the cells of the 

 organism. Again, with regard to the source of the anti- 

 toxine, some hold that it is produced by the living cells 

 under the stimulus of the toxine, whilst others look upon 

 it as a modified toxine. The bulk of evidence recently 

 brought forward is, however, strongly in favour of the 

 view that the two bodies unite in vitro to form a compound 

 inert towards the living tissues, there probably being in 

 the toxine molecule an atom group which has a specific 

 affinity for the antitoxine molecule or part of it, and that in 

 no sense is the antitoxine molecule a modified toxine mole- 

 cule. We shall consider the facts in favour of this view, 

 and in doing so we must also take into account the anti- 

 sera of the vegetable toxines, of snake poisons, etc. 



When toxine and antitoxine are brought together in 

 vitro it can be proved that their behaviour towards each 

 other resembles what is observed in a simple chemical 

 union. The test which is the indication of the neutralisa- 

 tion of the toxine by the antitoxine, is that when the 

 resultant body is injected into a susceptible animal no 

 symptoms occur. As in chemical union a definite period 

 of time elapses before combination is complete. C. J. 

 Martin and Cherry and also Brodie have shown, that in the 

 case of diphtheria toxine and in that of an Australian snake 

 poison the molecules will pass through a colloid membrane 

 (p. 157), whilst those of the corresponding antitoxines will 

 not. Now if a mixture of equivalent parts of toxine and 

 antitoxine is freshly prepared and at once filtered, a certain 

 amount of toxine will pass through, but the longer such 



