266 PHYSIOLOGICAL CHEMISTRY. 



munized animal has acquired the property of chemically com- 

 bining with or in some manner neutralizing the action of the 

 poison. That something akin to a chemical action is here in 

 question is shown by the fact brought out by further experi- 

 ments that certain proportions must be observed in the mixing 

 of the serum and toxic substance just as in the complete neu- 

 tralization of an acid by an alkali. It was further found that 

 this combination may be hastened by heat and retarded by 

 cold, which is true of most chemical reactions. The behavior 

 is also specific; that is, the animal immunized against the cas- 

 tor bean poison is not immunized thereby against other veget- 

 able toxic substances, as abrin for example, and the serum of 

 the animal will not, in vitro, neutralize the toxic abrin solution. 

 The same general condition has been recognized in connec- 

 tion with other immunizations and the characteristically spe- 

 cific nature of the anti body produced in the serum has been 

 shown beyond question. The anti bodies protective against 

 diphtheria have no effect against the toxins of tetanus or other 

 disease and vice versa. With such facts established, inquiry 

 was naturally directed toward the question of the ch'emical 

 nature of these substances and to the question of their mode 

 of action. In the voluminous discussions which have been 

 carried on over these points it is not always easy to distinguish 

 between observed facts and stoutly maintained theories. 



GENERAL CHARACTER OF THE ANTI BODIES. 



Antitoxins Proper. Foreign harmful agents gaining ac- 

 cess to the blood may be of several kinds. Some of these are 

 soluble toxic compounds, products of cell action, which in 

 their behavior bear some relation to strong alkaloidal poisons. 

 Many of these toxins are produced by bacteria in the animal 

 body during the progress of disease and the symptoms ob- 

 served are often due to the action of these poisons rather than 

 to mechanical disturbances brought about by the bacteria di- 

 rectly. The toxins as soluble products have the power of 

 wandering with the blood stream and thus reaching particu- 



