TOXiyS AND ANTirOXIXS 177 



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

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

 understanding the existence of an almost limitless number of specific 

 distinctions between proteins. Abderhalden, indeed, calculates that 

 The 20 amino-acids we find in proteins could form at least 2,432, !)02,- 

 008,176,640,000 different compounds, and this without including pos- 

 sible compounds varying in (luantitative relations. A contribution to 

 the chemical basis of specificity has been made by Kossel,^-'' who finds 

 certain relations in the proportions and groui)ings of the scanty num- 

 ber of amino-acids that make up the protamines and histones of sperm 

 to be characteristic of the sperm of certain species and families. 



In the subsequent discussion of the various reactions of immunity 

 tlie subject of specificity will receive further consideration. Of these 

 reactions, one of the simplest and most studied is that of 



TOXINS AND ANTITOXINS 



In the preceding chapter on the bacteria and their products the 

 nature of the true toxins was defined, and attention was called to the 

 fact that one of their most important characteristics is that immuniza- 

 tion of animals against them leads to the accumulation in the blood 

 of substances capable of neutralizing their poisonous action. Such 

 true toxins are produced especially by the diphtheria bacillus and the 

 tetanus bacillus; also, but less strikingly, by B. pyocyaneus, B. hotu- 

 linus, and possibly by a few others. In addition to these, numerous 

 l)aeteria produce hemohjtic poisons which seem to have properties sim- 

 ilar to the toxins; and there are also toxins produced by plants (abrin, 

 ricin, crotin, and mushroom poisons) and by animals (snake venom, 

 scorpion and spider toxin, and eel serum). Against all of these, true 

 antitoxins may be obtained by the immunization of animals. 



Ehrlich's Conception of Toxins and Antitoxins. — According to 

 Ehrlicirs theory, the action of toxins upon cells is purely chemical. 

 A toxin unites with a cell because some chemical group in the molecule 

 of toxin has a chemical affinity for some particular group in the cell 

 protoplasm. For convenience in description names have been given 

 to these groups; the group of the toxin that combines with the cell 

 has been called the haptopJiorous group, or haptophore, while the 

 group in the protoplasm that combines with the toxin is known as 

 the receptor.*^ It has been found that after being kept for some 



- 42bZeit. physiol. Chem., 1013 (88), 10:3. 



43 Ehiiich has used certain diatrrams to illustrate these various groups and 

 their relations to the cells and to one another, which are generally used in ex- 

 plaining his theory. From a teaching standpoint they liave seemed to be im- 

 desirable, in that tlie student soon comes to ascribe physical properties and 

 appearances to wliat should I)e considered as chemical combinations. The toxo- 

 phore group becomes '"the black fringed end of tlie toxin." etc. To one accus- 

 tomed to thinking in chemical terms there is no difficulty in following the litera- 

 ture and understanding the reactions as chemical reactions, which thev arc. 

 12 



