166 



IMMUNITY. THEORIES OF IMMUNITY 



variations in the arrangement of the amino-acids in a protein molecule 

 which the great number of these radicals provides, there is no difficulty 

 in understanding the possibility of an almost limitless number of specific 

 distinctions between proteins. 



It may be stated, however, in general, that immunologic reactions, 

 such as that of anaphylaxis, are as delicate in distinguishing between 

 proteins as are chemical analyses. Distinctions may be made by these 

 reactions with quantities too small for making accurate chemical de- 

 terminations. 



In succeeding chapters we shall consider, first, the different kinds of 

 immunity, as dependent upon the presence of various factors, and then 

 the role played by the phagocytes and the body-fluids in immunity, 

 with a more detailed consideration of the various antibodies. 



It may be useful here to draw up in tabular form a list of the various 

 antigens and antibodies with which we are mainly interested in that 

 portion of immunity involving infection with vegetable or animal para- 

 sites, and the products of their metabolism or degeneration (Fig. 43). 



ANTIGENS 

 Toxins: 



1. Soluble bacterial toxins (diph- 



theria and tetanus toxins, etc.). 



2. Phyto- (vegetable) toxins (ricin, 



abrin, etc.). 



3. Simple zoo- (animal) toxins; 



(snake, spider, toad venoms). 



4. Complex zootoxins, as snake 



venom, requiring complement 

 for action. 



Enzymes or ferments (rennin, lipase, 

 etc.). 



Precipitogenous substances (soluble ani- 

 mal and vegetable proteins). 



Agglutinogenous substances (bacteria, 

 erythrocytes, etc.). 



Opsonigenpus substances (bacterial en- 

 dotoxins or aggressins?). 



Cytolignequs substances: 



1. Vegetable cells (bacteria). 



2. Animal cells (erythrocytes, sper- 



matozoa, kidney tissue, etc.). 



ANTIBODIES 

 Antitoxins : 



1. Antitoxins (diphtheria and 



tetanus antitoxins, etc.). 



2. Anti- (phyto-) toxins (antiricin, 



antiabrin, etc.). 



3. Anti- (zoo) toxins (antivenins). 



4. Antihemolysins, etc. 



Anti-enzymes (antirennin, antilipase, 



etc.). 

 Precipitins. 



Agglutinins. 



Opsonins (acting singly or with comple- 

 ment) . 

 Cytolysins: 



1. Bacteriolysins. 



2. Hemolysins, spermatolysins, 



nephrolysins, etc. 



