126 BACTERIOLOGY FOR NURSES 



for example, that substance is a toxin and it is sufficiently abundant 

 and powerful, many receptors may be thus lost and many cells 

 damaged . Symptoms of the specific disease may present themselves 

 and death may ensue. On the other hand, if the injured cells 

 possess sufficient vitality the loss of one or more receptors will 

 stimulate them to an immediate attempt to repair the damage. 

 Since nature is always lavish in her processes of repair it may hap- 

 pen that not only are the lost receptors replaced but a large num- 

 ber are added. These excess receptors having no place for attach- 

 ment to the cell are thrown off into the blood stream. All possess 

 the same structure as the original ones. Consequently when they 

 meet in the blood stream with the same kind of substance which 

 caused their production, their antigen, they are capable of com- 

 bining with it and rendering it harmless before it is able to attack 

 the body cells. In diphtheria and tetanus the antigen is the toxin 

 of the bacteria, and the cast-off receptors produced as a result 

 of its action constitute antitoxin. 



It should be noted that an excess production of receptors or 

 antibodies occurs only as a result of the chemical union of a receptor 

 with a poisonous substance ; the assimilation of food material is 

 of benefit to the cell ; consequently the receptors remain unharmed. 



Three Orders of Antibodies. First Order (Antitoxins). The 

 simplest receptor of the cell molecule is conceived as possessing 

 a single arm or haptophore for union with a correspondingly simple 

 food molecule. A toxin molecule is imagined as possessing two 

 portions, one the haptophore especially adapted to fit this simple 

 receptor, and a second, the toxophore portion in which its toxic 

 power resides. The cast-off receptors of this order constitute 

 antitoxin. Fig. 21. 



Second Order (Agglutinins, Precipitins) . All diseases are 

 not produced by soluble toxins, and furthermore the production of 

 antitoxin does not explain such phenomena as the agglutination 

 of bacteria and the dissolving property of certain sera. Accord- 

 ingly Ehrlich modified his theory and assumed that while simple 

 molecules of food might be readily assimilated by the simple cell 

 receptor, other more complex molecules might require some form 



