484 IMMUNITY. 



or outside the animal body the action of the homologous 

 serum has a dual character, in other words, two substances 

 are concerned. One of these is the specific substance 

 " immune-body " developed in the serum, the other a sub- 

 stance present in normal serum ; by a temperature of 

 60 C. the latter is readily destroyed, while the former is 

 practically unaffected, at least for some time. A serum thus 

 heated also retains its agglutinative action, but there is still 

 a dispute as to whether the agglutinine and the immune- 

 body are the same. Some observers, e.g., Pfeiffer, Kolle, 

 and Ehrlich consider that the agglutinative and preventive 

 action are independent of one another, whilst Gruber and 

 Durham consider them intimately related and probably due 

 to the same substance. It appears that agglutination is 

 not essential to the possession of preventive power, but on 

 the other hand it is very doubtful whether high agglutina- 

 tive power ever occurs quite apart from the latter. In view 

 of all the facts the appearance of the agglutinative property 

 is most probably to be regarded as a phenomenon pre- 

 judicial to the corresponding organism, and thus in its 

 nature is to be associated with the process of immunisation. 

 If Ehrlich's theory with regard to lysogenic action (vide 

 infra) is correct, it will in all probability apply to the de- 

 velopment of agglutinines. It will remain to be determined 

 whether the immune-body sometimes acts as an agglutinine 

 or whether the two substances are distinct. 



Lysogenic Action towards Blood Corpuscles. These striking pro- 

 perties are, however, not peculiar to bacterial immunity. Bordet has 

 recently shown that similar reaction's can be acquired by the serum of 

 one animal towards the red corpuscles of another of different species. 

 Instances had previously been known of the serum of one animal 

 causing agglutination of the red corpuscles of another or producing 

 their solution, but these powers are not generally possessed. The 

 experiments of Bordet, however, show that such properties may be 

 acquired, and may reach a high degree. This was effected by inject- 

 ing defibrinated blood of the rabbit into the peritoneum of a guinea- 

 pig. After a number of injections the serum of the latter when added 

 to defibrinated rabbit's blood dissolves the red corpuscles with great 

 rapidity. A point of special interest is that here again two substances 

 are concerned. When the serum is heated to 55 C. it loses its dis- 



