430 TETANUS 



tetanus as with diphtheria toxin, the action of an acid is to 

 cause an apparent disappearance of toxicity, but if before a 

 certain time has elapsed the acid be neutralised by alkali, then a 

 degree of the toxicity returns. 



As with other members of the group, nothing is known of the 

 nature of tetanus toxin. Uschinsky has found that the tetanus 

 bacillus can produce its toxin when growing in a fluid containing 

 no proteid matter. The toxin may thus be formed independently 

 of the breaking up of the proteins on which the bacillus may be 

 living, though the latter has a digestive action on proteins. 

 There is evidence that peptic digestion and toxin formation are 

 due to different vital processes on the part of the tetanus 

 bacillus. 



The toxin is one of the most powerful poisons known. Even with a 

 probably impure toxalbumin Brieger found that the fatal dose for a 

 mouse was - 000'5 of a milligramme. If the susceptibility of man be the 

 same as that of a mouse, the fatal dose for an average adult would have 

 been "23 of a milligramme. Animals differ very much in their suscepti- 

 bilities to the action of tetanus toxin. According to v. Lingelsheim, if 

 the minimal lethal dose per gramme weight for a horse be taken as unity, 

 that for the guinea-pig would be 6 times the amount, the mouse 12, the 

 goat 24, the dog about 500, the rabbit 1800, the cat 6000, the goose 

 12,000, the pigeon 48,000, and the hen 360,000. 



A striking feature of the action of tetanus toxin is the 

 occurrence of an incubation period between the introduction of 

 the toxin into an animal's body and the appearance of symptoms. 

 This varies according to the species of animal employed, the path 

 of infection, and the dose given. In the guinea-pig it is from 

 thirteen to eighteen hours, in the horse five days, and the in- 

 cubation is shorter when the poison is introduced into a vein 

 than when injected subcutaneously. In man the period between 

 the receiving of an injury and the appearance of tetanic symp- 

 toms is usually from two to fourteen days, but this period 

 may be lengthened, and the bacilli may remain a con- 

 siderable time shut up in a wound before producing effects. 

 The longer the incubation period, the more favourable is the 

 prognosis, and in chronic cases spontaneous recovery is not 

 uncommon. 



With regard to the action of the toxin, it has been shown to 

 have no effect on the sensory or motor endings of the nerves. 

 It acts solely as an exciter of the motor cells in the spinal cord, 

 the nerve storm being often precipitated by peripheral irritation. 

 The motor cells in the pons and medulla are also affected, and 

 to a much greater degree than those in the cerebral cortex. 



