CHAPTEE VII. 



ANTIBODIES IMMUNITY EHRLICH'S SIDE-CHAIN THEORY 

 THE WASSERMANN SERUM TEST. 



ANTIBODIES. 



Toxins and Antitoxins. It has already been stated that some 

 pathogenic bacteria secrete very powerful soluble toxins which enter 

 the general circulation. Whenever such toxins circulate in the blood 

 there is a tendency to the formation of bodies which neutralize them, 

 and bring about a cure, provided that the toxins are not overabun- 

 dant and have not already done irreparable damage. When tetanus 

 toxins are in the system of a horse they are usually generated so 

 quickly and abundantly that before they can be neutralized by natural 

 or artificial means irreparable damage has been done to some part of 

 the body, generally the central nervous system. The bodies which 

 neutralize the soluble toxins are called antitoxins. Their effect can 

 be best understood by comparison with the well-known chemical 

 reaction between acids and alkalies. There is a disease common in 

 man, and sometimes found in the domestic animals, which is char- 

 acterized clinically by the secretion of sugar in the urine and by 

 the inability of the body to properly split up and utilize this sugar. 

 Consequently, sugar finds its way into the blood, and from this carbo- 

 hydrate a large amount of organic acid is formed. No being could 

 exist with a large amount of free acid in the blood, so the system at 

 once corrects the defect by furnishing to the blood a large amount 

 of ammonia to neutralize the organic acids. Somewhat similarly the 

 antitoxins neutralize the toxins. Just as hydrochloric acid can be 

 neutralized in the test-tube with ammonia, so can a soluble toxin 

 be neutralized with its antitoxin. The principle is the same, although 

 the process is a much more complicated one than the neutralization 

 of an acid by an alkali. The toxin-antitoxin mixture can be injected 

 into a susceptible animal without producing any ill effects. Thus 

 the formation of antitoxins is another means by which the body 

 protects itself against pathogenic bacteria; that is, against one of 

 their most important products, the toxins. 



Agglutinins, Lysins, Precipitins. If cholera spirilla are injected 

 into the peritoneal cavity of an animal which is not susceptible to 

 them, and from time to time removed by the aid of small capillary 

 pipettes, it will be noticed that the spirilla soon lose their motility, 

 become glued to each other, forming small lumps, indistinct in out- 



