FERMENTATION 223 



between toxine and antitoxine is quantitative. These 

 results, obtained by test-tube experiments, have been 

 confirmed by observations on living animals. Thus it 

 was established that a fixed quantity of toxine is neu- 

 tralized by a fixed quantity of its specific antitoxine. 



Chemical substances affect only those tissues with 

 which they are able to come into chemical contact. 

 They must first reach the tissue. This general law is 

 illustrated by the experiments of Donitz with tetanus 

 toxine. 1 When the toxine is injected directly into 

 the circulation and immediately followed by a chemi- 

 cally equivalent amount of antitoxine, the animal is 

 not poisoned ; all the toxine circulating in the blood 

 is neutralized. When the same neutralizing dose is 

 injected eight minutes after the toxine, death occurs 

 from tetanus exactly as if no antitoxine had been used. 

 In these eight minutes a lethal quantity of toxine 

 must have left the blood and entered the tissues. 

 This toxine which has entered the tissues may still 

 for a time be withdrawn by injection of the specific 

 antitoxine in quantities much greater than the simple 

 neutralizing dose. The longer the delay, the larger 

 the saving dose. But after a fixed interval, or " period 

 of incubation," no amount of antitoxine, however 

 large, will prevent tetanus. There must, therefore, 

 be present in the brain or cord (the organ princi- 

 pally affected by tetanus toxine) certain atom groups 

 which, like the antitoxine, have a chemical affinity 

 for the toxine. At the close of the period of incuba- 



1 Donitz : Klinisches Jahrbuch, 1900, vii. 



