60 IMMUNITY 



bodies, combine with them and that when complement acts upon 

 this union toxic substances are set free. 



In explaining all infectious diseases on this basis one assumes 

 that sometime in life a person has been sensitized by bacteria or 

 their proteins so that he is receptive for a virulent germ when 

 this has overcome the primary external bodily defenses. It is also 

 to be considered the modern explanation of diatheses. 



McKail divides anaphylaxis as follows: 



Natural Anaphylaxis, depending upon 



a. Species of animal, for example cholera in man, anthrax 

 in cattle, glanders in horses. 



b. Age diphtheria in children, erysipelas in the elderly. 



c. Individual to white of egg, or blood serum, even by inges- 

 tion ("one man's meat is another man's poison"). 



Acquired Anaphylaxis, depending upon 



a. An attack of disease, erysipelas, diphtheria. 



b. The injection of dead cells, tuberculin. 



c. Injection of nitrogenous matter, blood serum and egg-white. 



_ Complement Fixation. Hemolysis occurs when the serum of 

 a rabbit immunized against washed sheep's red blood cells is mixed 

 with fresh washed sheep's corpuscles in the presence of complement. 

 If, however, complement be absorbed in any way a solution of the 

 coloring matter of the red cells will not occur in this mixture. 

 Complement will combine with anti-body in the presence of antigen. 

 This fact has been taken advantage of in determining both the 

 nature of antigen and the presence of anti-body. Its most important 

 practical use is in syphilis, to the diagnosis of which Wassermann 

 applied it, and the Wassermann test is for the presence of syphilitic 

 anti-body in the blood serum of syphilitics. This test is positive 

 from the initial lesions all during life unless the patient has been 

 successfully treated. Indeed the parasyphilitic states also give it. 

 The principles of the test are also used for determining the pres- 

 ence of tuberculous, leprous, typhoid and other anti-bodies. 



