ACTION OF ANTITOXIC SERUM. 441 



These investigations are specially instructive, as the 

 poisons, both as regards their local action and the general 

 toxic phenomena produced by them, present an analogy to 

 various toxines of bacteria. 



Action of Antitoxic Serum. In order to protect an 

 animal from the toxine, the antitoxic serum must be added 

 in a definite proportion. It has no cumulative action, or 

 in other words, it cannot neutralise a larger amount of 

 toxine simply by being left in contact with it for a longer 

 period of time. Experiment shows that there is an antago- 

 nistic action between the toxine and the antitoxine, but the 

 nature of this action is not yet fully known. We know 

 almost certainly that the action is not a simple chemical 

 one comparable with the action of base and acid, but that 

 vital processes are involved, so that we may call the anta- 

 gonism a physiological one. For example, it was found 

 by Roux and Vaillard that if too large doses of the toxine 

 were administered in immunising a horse, the blood serum 

 might lose its antitoxic power and actually become toxic 

 for another animal. Buchner found that a mixture of 

 antitoxine and toxine could be prepared so as to be 

 practically harmless for mice, but have a toxic action for 

 guinea-pigs. In this connection, however, it must be borne 

 in mind that the natural resistance of the guinea-pig against 

 tetanus toxine is less than that of the mouse, and that anti- 

 toxine as well as toxine has a relative value. The anti- 

 toxine in all probability acts on the tissues susceptible 

 to the toxine and makes them immune to the toxine, 

 or toxine-proof, but we can say little further than this. It 

 has been found that immunity lasts for some time after the 

 antitoxine has disappeared from the blood. The very 

 small amount of antitoxine which is, in some cases, suffi- 

 cient to protect from a proportionately large dose of toxine, 

 shows the action to be of a very subtle nature. A serum 

 may have high antitoxic power without possessing any 

 bactericidal action against the corresponding bacterium. 

 The diphtheria and tetanus bacilli, for example, flourish 

 well in their respective anti-sera. The fact that these sera 



