PRACTICAL APPLICATIONS 411 



the mixture will survive, whilst the other will develop tetanic 

 symptoms and die. Even if other pathogenic bacteria are present 

 the indications are usually clear, since spasms will commonly 

 develop (in the animal which has received no antitoxin) before the 

 lethal issue. It is best to use a broth culture for this test, so that 

 there may be a good development of toxins. 



The nature of the toxins of tetanus have been already mentioned. 

 There are two, both exotoxins the real poison, tetanospasmin, and 

 tetanolysin. Tetanospasmin is readily prepared by cultivation of 

 the organism in pure culture in almost any medium under anaerobic 

 conditions. It is even more fragile than diphtheria toxin, being 

 rapidly rendered inert in a few days if exposed to air at ordinary 

 temperatures. It is destroyed in eight to eighteen hours by 

 sunlight, by a temperature of 55 C. in one and a half hours, and by 

 exposure to agents such as alcohol, potassium permanganate, and 

 trichloride of iodine. It can be preserved by means of dilute 

 carbolic acid (0-6 per cent.) or chloroform without much loss. 

 Inert solutions have in general powerful immunizing properties, 

 the toxin being converted into toxoids, and not absolutely 

 destroyed. 



It can be prepared so as not to give the reactions for proteid, 

 and is formed when the bacillus is grown on Uschinsky's proteid- 

 free medium. Its potency is enormous. Thus Vaillard prepared 

 a toxin of which the lethal dose for a guinea-pig was 0*001 c.c., 

 containing about 0*000025 gramme of solid matter, only a small 

 portion of which was pure toxin. Brieger and Cohn calculated 

 that the lethal dose of an (impure) toxin for a man was 0-00023 

 gramme. 



The effect of tetanus toxin is manifested almost solely on 

 the central nervous system, and the post-mortem lesions are 

 practically confined to the ganglionic cells, especially of the 

 anterior cornua. It appears probable that there is no direct 

 action on the nerves themselves, but the toxin, like the virus of 

 rabies, reaches the central nervous system mainly, if not entirely, 

 by ascending the nerves leading from the area of inoculation. 

 According to Meyer and Ransom, toxin which gains access to the 

 blood only affects the brain by entering the peripheral nerves via 

 the nerve endings, especially the end-plates, but this is not 

 universally accepted. As in the case of rabies, the richer the area 

 of inoculation in nerves, the more powerful the action of the toxin 

 and the shorter the period of incubation. The brain and cord are 



