2 20 MANUAL OF BACTERIOLOGY. 



that may be present. The toxin molecule, b, has its toxophore 

 group represented by the fringe-like end, d. If the cell receptor 

 becomes detached from the cell, its haptophore, e, may unite 

 with a toxin molecule as readily as when the receptor is still 

 attached to the cell. Such a detached receptor constitutes a 

 molecule of antitoxin. 



As the side-chains or receptors of the protoplasm are es- 

 sential to its existence, their combination with the toxin-, 

 through its haptophore, results in destruction of the molecule. 

 But if the damage be not too serious, the protoplasm is stimu- 

 lated to produce numerous similar side-chain groups — to an 

 overproduction of these, in fact. As not all of these are neces- 

 sary for the performance of its functions, the superfluous ones 

 are thrown off into the surrounding serum. It is well known 

 that many cells of the body exhibit analogous heightened acti- 

 vities under stimulating iniJuences, as pointed out by Weigert. 

 If such free side-chains or receptors combine with the .hap- 

 tophorous groups of the toxin, the latter is no longer able to 

 combine with the protoplasm of the cells. Thus they act as a 

 kind of buffer in protecting the protoplasm from the attacks of 

 the toxins. These free, cast-off receptors constitute the 

 antitoxic part of the serum as stated. 



Numerous experiments have been made which illustrate 

 the probable chemical nature of antitoxin action. A fatal 

 dose of diphtheria or tetanus toxin may be neutralized outside 

 of the body by mixing it with its appropriate antitoxin. In- 

 jection of the mixture shows it to be innocuous to animals. 



The manner in which toxins combine with protoplasm has 

 been shown in the case of tetanus toxin. The filtrate from 

 cultures of tetanus bacilli will kill guinea-pigs, presumably 

 by damage to the central nervous system. The same filtrate 

 rubbed up with brain or spinal c ird has been found to have lost 

 its toxic properties. It may be assumed that the poison has 

 combined with the protoplasm of the cells. 



