156 A MANUAL OF BACTERIOLOGY 



nerve-tissues by means of their haptophore groups ; this 

 after a time brings the cells within the sphere of influence 

 of the toxophore groups, and after a certain incubation 

 period toxic symptoms ensue. The affinity of tetanus 

 toxin for nerve tissues may be shown in another way. If 

 fresh guinea-pig brain be emulsified with tetanus toxin, 

 the emulsion will be found to be innocuous on injection, 



FIG. 31. Diagrammatic scheme to represent the union of toxin 

 (black) with the cell. In A the toxin is attached to the pro- 

 toplasm by the union of the haptophore and receptor groups. 

 In B the toxophore and toxophile groups have also united, 

 and poisoning now ensues. 



owing to a combination between the two having taken 

 place. The cerebral cortex of a highly susceptible animal 

 (e.g. mouse) has a marked neutralising power, of a less 

 susceptible animal (e.g. rabbit, fowl) a feebler, and of an 

 insusceptible animal (e.g. frog, tortoise) no neutralising 

 power. 1 Moreover, both diphtheria and tetanus toxins 

 may be converted into non- toxic modifications (" toxoids ") 

 which to some extent retain the power of immunising 

 and of producing antitoxin on inoculation, and of com- 

 bining with antitoxin : that is to say, according to Ehrlich, 



1 The combination of brain matter with tetanus toxin seems to be 

 specific and of the same order as that between antitoxin and toxin. 

 See Noon, Journ. of Hyg., vol. vii, 1907, p. 101, and Besredka and 

 Bordet, Ann. de Vlnst. Past., xvii, 1903. 



