20 APPLIED IMMUNOLOGY 



as distinguished from those naturally existing in the 

 normal animal, are called immune bodies, and the 

 animal is said to be immune to the particular antigen 

 in question. 



Various Forms of Antibodies 



(a) Toxins and Antitoxins, — Toxins are the solu- 

 ble products of bacterial and plant growth, also the 

 secretion of certain reptiles, and in the case of some 

 bacteria are the means through which the deleterious 

 effects of the bacteria are brought about. Antitoxins 

 are specific substances produced in the blood-serum 

 whereby the action of bacterial toxins is antagonized. 



{h) Agglutinins. — JVIany forms of bacteria, when 

 introduced into the body, stimulate the body-cells to 

 produce specific substances called agglutinins, which 

 have the property of causing the bacteria to lose their 

 motility and to mass together in clumps. This phe- 

 nomenon is of great practical importance in the diag- 

 nosis of certain bacterial infections. For example, 

 the blood- serum of a patient affected with typhoid 

 fever contains agglutinins, so that when it is brought 

 in contact with typhoid bacilli agglutination of the 

 latter will take place. 



{c) Precipitins, — Precipitins are closely allied to 

 agglutinins, and are antibodies which bring about the 

 precipitation of soluble foreign proteins. They also 



