THE PROTECTIVE SUBSTANCES OF THE BLOOD. 377 



but restrict this term to such masses of iron which deflect the light- 

 ning from a particular point, so we must restrict the term antitoxin 

 to those toxinophile groups which circulate in the blood and thus 

 deflect the poison from the susceptible organs. The toxinophile 

 groups present in these susceptible organs are not toxin deflectors but 

 toxin attr actors. 



The theory also explains why the property of producing antitoxins 

 is restricted to certain products of metabolism of living cells. All 

 experiments to produce antibodies by means of chemically well de- 

 fined toxic substances, such as morphine, strychnine, saponin, etc., 

 have failed. 



If we bear in mind that the distribution of these substances in 

 the organism takes place without chemical union and therefore with- 

 out the intervention of receptors, the negative result of these experi- 

 ments will not surprise us. The property of forming antitoxin is 

 possessed only by such substances as possess a group able to unite 

 with the side-chains or receptors which effect assimilation. It must 

 be remembered that all the poisons which excite the production of 

 antitoxin are highly complex products of animal and vegetable cells, 

 which in their chemical properties approach the true albumins and 

 peptones. In 1897, by means of my theory, the production of anti- 

 toxin and the binding of foodstuff were first brought into connec- 

 tion. At that time nothing was known of the fact that even ordinary 

 foodstuffs are capable of an analogous action. 1 have therefore been 

 able to regard as an agreeable confirmation of my views the circum- 

 stance that this consequence of my hypothesis has actually repeatedly 

 been demonstrated within the past year, especially by Bordet. 



If animals are injected with milk, it is found that their serum 

 gains the property of precipitating the milk in curds. This precipita- 

 tion is also strictly specific, since numerous experiments show that 

 the coagulating serum obtained by treatment with goat milk coag- 

 ulates only goat milk, and not the milk of other species, as, for ex- 

 ample, that of women or cows. 



The results are similar if animals are injected with other albumi- 

 nous substances, e.g., with the sera of different species or with egg 

 albumin. In this case in the serum of the animal there develop sub 

 stances (termed coagulins or precipitins) which specifically precipitate 

 the corresponding kind of albumin. 



Deviations from the law of specificity occur only in so far as the sera of 

 closely related animal species contain substances more or less similar Thus 



