VI 



trary, the agglutinating power having after another in- 

 jection of agglutinin again fallen down to the normal tiler, 

 1,2, the injection of 75 cc. of culture was followed by 

 a great reaction. This corresponded to the curve, which 

 is obtained in the case of actively immunised animals. 

 The maximum 158,8 was reached on the llth day, and 

 when the tiler on the 4 /s had fallen down to 100 a new 

 injection of culture was made (120 cc. 24h). This 

 was followed by a fall, apparently in direct continu- 

 ation of the preceding, and then a new rise with maxi- 

 mum at 10000 occurred. 



Is thus appears, that this animal is not influenced 

 by B. typhos. cullure when its serum has an agglutinating 

 power of 15, originating from introduced agglutinin. 



But after Ihe disapperance of all this, and the blood 

 having only ils small normal agglutinating power, a 

 marked reaction is produced by the same factors. This 

 is also the case during active immunisation, the animal 

 itself producing the agglutinin. The contrast between 

 these two conditions appears clearly from the curve. 



The difference between active and passive immunisation 

 shown by these observations is very distinct, and we are 

 now met wilh the problem, what is the cause to this 

 difference. 



From our observations aboul the neutralisation in 

 vitro of toxins and anlitoxins it is not possible to con- 

 clude what is going on in an organism during active 

 immunisation. This was already emphasized by Salo- 

 monsen and Madsen 1 ) in the case of active immuni- 

 salion of horses against diphtheria. Take for instance 



Salomonsen & Madsen: Kecherches sur la marche de 1'immunisation active 



centre la diphterie. 



Bulletin de 1'Acad. Royale des Sciences et des Lettres de Danemark. 1896. 



30 



