THEORIES OF IMMUNITY. 



In this case, the toxine molecule is to be rep- 

 resented as before : 



The toxine molecule =H+T+X, 

 The cell molecule =H-KN"+X, 



in which the X may be supposed to represent 

 the atom-group concerned in nutrition, and X 

 other atom-groups not necessary in the expres- 

 sion of this reaction. 



Then the H groups in the two molecules com- 

 bine (the combination appearing thus: 



/H+T+X 



\H+N+X) 



and a double action may be supposed to take 

 place; on the one hand the T group will exert a 

 more or less irritant action on the cell molecule, 

 and on the other hand the H group of the tox- 

 ine molecule will take up the H. group in the cell 

 molecule. Xow, under ordinary conditions this 

 H group of the cell molecule is necessary for 

 the proper growth and metabolism of the cell, — 

 if it be taken up for something else, the cell 

 molecule will die or else its II group must be 

 replaced. This replacement occurs in the case 

 we are supposing, and takes place in excess; 



