180 A MAISTUAL OF BACTERIOLOGY 



With those organisms which produce potent toxins, like 

 the diphtheria and tetanus bacilli, it is customary to grow 

 the organism in a fluid medium so that an active and 

 virulent toxin is obtained. The culture is then filtered 

 through a Berkefeld or Pasteur-Chamberland filter and 

 the toxic filtrate inoculated subcutaneously into an 

 animal, generally a horse, commencing with sub-lethal 

 doses. 



The dose of toxin can be gradually increased, and con- 

 currently with the increase in insusceptibility the blood- 

 serum acquires antitoxic properties. The treatment is 

 tedious, and the activity of the antitoxic serum is largely 

 dependent upon the amount and activity of the toxin 

 injected. The requisite degree of strength having been 

 attained, the horse is bled with aseptic precautions, the 

 blood is allowed to coagulate, and the serum is bottled 

 for use. Antitoxin may be obtained in a concentrated 

 form by " salting out " the globulin constituents of an 

 antitoxic serum (p. 197), and a dried product may be 

 prepared by evaporating the serum to dryness in vacua 

 at 40 C. (10 c.c. serum = I grm. dry residue). 



The mode of production of the antitoxin by the in- 

 jection of the toxin has been the subject of discussion. 

 By some it has been supposed that the antitoxin is 

 modified toxin, the modification being brought about by 

 the vital activities of the cells. But the amount of anti- 

 toxin produced does not necessarily bear any relation to 

 the quantity of toxin injected. Woodhead records in- 

 stances in which the amount of antitoxin formed amounted 

 to 40,000 times the equivalent amount of toxin injected ; 

 bleeding the animal only temporarily reduces the anti- 

 toxin content of the serum, and substances which increase 

 the secretory properties of glandular cells, such as pilo- 

 carpihe, enormously increase the output, so to speak, of 

 antitoxin. 



