THE BLOOD. 



215 



and still be capable, by means of its haptophore group, of combining 

 with antitoxin. For a poison to be toxic to an organism that is, 

 in order that the toxophore group be able to act destructively on a 

 cell it is necessary for the liaptophore group of the poison to com- 

 bine with the cell. The side-chains are able to combine with the 

 greatest variety of foreign substances and convert them into nour- 

 ishment suitable to the requirements of the active central body. 

 These side-chains are comparable to the pseudopodia of the amoeba 

 which engulf food particles and assimilate the same for the imme- 

 diate use of the organism. In order that any substance may com- 

 bine with these side-chains, it is necessary that certain very definite 

 relations exist between the combining group of the 'substance and 



Fig. 61a-- 



(J. D. 



-Stages in Widal Reaction. 



(After ROBIN.; 



that of the side-chain. The relation m-ust be that of lock and key; 

 that is, the two groups must fit accurately. 



AGGLUTININS. 



If we cultivate a vibrio of cholera upon gelatin, and after 

 twenty-four hours put the culture in a saline solution 1 to 100, we 

 obtain a homogeneous and stable emulsion, in which the vibrios 

 retain their activity. If to this emulsion we add a small quantity 

 of blood-serum (of a rabbit or guinea-pig) strongly immunized 

 against the vibrio of the emulsion by the intra-peritoneal injection, 

 we will see under the microscope that the vibrios lose their mobility 

 and unite in masses of greater or less size, agglutinate, so to speak. 

 This agglutination augments until the mass becomes voluminous. 

 This agglutination is not a necessary result of the vitality of the 

 vibrios; it is just as easily produced with emulsions of dead vibrios. 



