ANTITOXIN. 5 



had been successively injected a great many times (more 

 than twenty or thirty times) with pure diphtheria toxin, con- 

 tinues to react to every injection as much as at the earlier 

 stages, provided the dose injected be gradually increased. 



The most important result, however, of the observations 

 on producing artificial immunity was the one elucidated by 

 Behring l and his collaborators; viz., that the blood and 

 blood serum of the immunised animals (diphtheria and 

 tetanus) when injected in certain proportion into otherwise 

 susceptible animals furnishes these latter with immunity, 

 and more than that, is capable of arresting and curing the 

 disease in the already infected animal. These classical 

 experiments of Behring and his collaborators on artificial 

 immunisation, and of using the blood serum of the immunised 

 animals as protective and curative (Heilsentm) agents 

 (Serumtherapie) form the basis of all subsequent observations 

 on antitoxin treatment in diphtheria and tetanus, and without 

 in the least decree wishing to minimise the merits of the 

 contributions of various observers like Babes (in rabies), 

 Tizzoni and Cettani (tetanus), Roux and Martin (diphtheria), 2 

 it is, I think, admitted that to Behring belongs the credit of 

 having fully grasped the meaning of, and established on a firm 

 experimental basis, the facts concerning artificial immunisa- 

 tion against tetanus and diphtheria, and the use of blood 

 serum of the immunised animals both as protective and 

 curative agents. In addition to this, Behring has clearly 

 established that the blood serum of an immunised animal 

 owes its antitoxic power to chemical substances ; that these 

 are present dissolved in the blood, as such and not as cellular 

 bodies ; that their action takes place outside {in vitro) as 

 well as in the body of an animal ; and that, therefore, the 

 production of acquired immunity, i.e., the presence of 

 antitoxin in the blood, has nothing and can have nothing 

 to do with mechanical phagocytosis as advocated by 



1 Behring, Die Blutserumtherapie bei Diphtherie und Tetanus, Zeitschr. 

 f. Hygiene, xii., p. i. 



Behring and Knorr, Ueber den Immunisirungswerth u. Heilwerth 

 des Tetanusheilserums bei weissen Mausen, Zeitschr. J. Hygiene, xiii. 



2 Tizzoni and Cettani, La Rif. med., T893, No. 131. 

 Roux, Annates de VInstitut Pasteur, Septembre, 1894. 



