Applies only to the bacterium or toxin used in its production.
Then we have the property of adaptation, in which the negative reaction may be changed into a positive; a given toxin may at first repel the cell, but by a gradual process the cell becomes accustomed to such a toxin and will move towards it.
By growing this bacillus in broth a toxin is formed which remains in solution and can be separated from the bacilli themselves by filtration.
The serum of the animal is tested from time to time against a known amount of toxin, i.e.
In the earlier experiments on smaller animals the potency of the toxin was modified for the first injections, but in preparing antitoxin for therapeutical purposes the toxin is used in its unaltered condition, the horse being the animal usually employed.