Artificial immunity against toxins 359 



International Congress at Budapest in 1894, the manifestation of 

 the toxic action of the venom after it has been heated along with 

 antitoxin, may be reconciled with the view that the combination 

 between the two substances, if such take place, must be very unstable. 

 This same remark may be applied to Wassermann's experiment. [377] 

 Therefore the great majority of observers, if not all, admit that the 

 antitoxin combines with the toxin to form an innocuous and unstable 

 substance which can be decomposed by heat and by other agents. 

 The researches on the action of antitoxins in vitro have had a 

 powerful influence in determining this view. 



We have already in Denys and van de Velde's 1 experiments an 

 indication of the direct action of certain antitoxins. These observers 

 showed that the serum of animals vaccinated against a Staphylococcus 

 is capable of neutralising in vitro a particular toxin to which van de 

 Velde gave the name of leucocidin. When it was added to a drop of 

 the exudation from a rabbit, this leucocidin in a very short time 

 destroyed the white corpuscles, by dissolving the cell content but 

 leaving the nucleus untouched. When Denys and van de Velde 

 prepared mixtures of leucocytes, leucocidin and antileucocidic serum 

 in vitro, the white corpuscles retained their normal condition for a 

 very long time. The leucocidin was, therefore, rendered inactive by 

 the direct influence of the corresponding antitoxin. These facts have 

 been confirmed by Bail 2 and other observers and even extended to 

 certain other microbial toxins. Thus, the Bacillus pyocyanaus pro- 

 duces a leucocidiu which kills the white corpuscles and dissolves 

 their contents 3 . With the object of facilitating experiments with 

 these leucocytic poisons and the corresponding antitoxic serums, 

 Neisser and Wechsberg 4 , of the Institute of Experimental Thera- 

 peutics at Frankfort, invented a method which allows us to observe 

 the phenomena of the destruction of the leucocytes and of the anti- 

 toxic power in test tubes, without having recourse to a microscopical 

 examination. They applied the fact, discovered by Ehrlich, that 

 living formed elements reduce methylene blue and, depriving it of its 

 oxygen, decolorise it. Leucocytes from aseptic exudations are intro- 

 duced into tubes and a weak solution (2%) of methylene blue is 

 poured on them. To prevent the re-oxidation of this colouring- 



1 La CeUule, Lierre et Lou vain, 1896, t. xi, p. 359 ; Ann. de Ilnst. Pasteur, Paris, 

 1896, t. x, p. 580. 



2 Arch.f. Hyff., Miinchen u. Leipzig, 1897, Bd. xxx, S. 348. 



3 Gheorghiewsky.^nn. de Flnst. Pasteur, Paris, 1899, t. xrn, p. 298. 



4 Ztschr.f. Hyg., Leipzig, 1901, Bd. xxxvi, S. 330. 



