BACILLUS TETANI 477 



the gelatin-liquefying ferment (peptonizing ferment) has nothing to 

 do with the toxin; it is quite distinct from it. 



Properties of Tetanus Toxin. Tetanus toxin is unstable. Exposure 

 of broth filtrates containing tetanus toxin to 55 C. for an hour and 

 a half, twenty minutes at 60 C., or five minutes at 65 C., reduces 

 the potency to a very considerable degree. 1 For the complete destruc- 

 tion of the toxin, however, considerable heating is necessary. The 

 toxin is particularly susceptible to light. According to Fermi and 

 Pernossi, 2 fifteen to eighteen hours' exposure to daylight destroys it. 3 

 Tetanus toxin is destroyed by gastric and by tryptic digestion. 4 Dried 

 tetanus toxin is more stable to physical agents and to heat than toxin 

 in solution. Morax and Marie 5 have shown that dried tetanus toxin is 

 not destroyed by an exposure to dry heat of 120 C. for fifteen minutes. 



Purification of Toxin. Tetanus toxin may be obtained in a partially 

 purified state by precipitating the broth in which it is contained 

 with saturated ammonium sulphate, dialyzing the salts from the 

 precipitate and drying the salt-free residue in vacuo. 6 The dried toxin, 

 if kept in a cool, dark place, remains potent for many months. 



Tetanus toxin is one of the most potent known: as little as 0.0001 

 c.c. of the toxic broth frequently kills a 15-gram mouse. Purified 

 toxin, prepared by precipitation with ammonium sulphate, will kill 

 a mouse of the same weight if but 0.00005 gram is injected. Man and 

 the horse are very susceptible to the tetanus toxin. Knorr 7 estimated 

 that a gram of horse was twelve times as susceptible to the tetanus 

 toxin as a gram of mouse, and three hundred times as susceptible as 

 a gram of hen. The reptilia are practically non-susceptible: toxin 

 injected into these animals circulates in the blood stream without 

 causing symptoms and it is finally eliminated. 



Action of Tetanus Toxin. Even when massive doses of toxin are 

 injected into susceptible animals, a latent period exists between the 

 time of inoculation and the appearance of symptoms, which can not 

 be reduced below eight hours. 8 The incubation period increases when 



1 Kitasato, Ztschr. f. Hyg., 1891, x, 267. 2 Ztschr. f. Hyg., 1894, xvi, 385. 



3 For a full discussion of the physical properties of tetanus toxin see Fermi and Per- 

 nossi, Centralbl. f. Bakt., 1894, xv, 303. 



4 Baldwin and Levene, Jour. Med. Research, 1901, vi, 120. 



5 Ann. Inst. Past., 1902, 419-420. 6 Brieger and Cohen, Ztschr. f. Hyg., 1893, xv, 8. 



7 Munchen. med. Wchnschr., 1898, 321. 



8 Courmont and Doyen, Arch, de Phys., 1893; Goldschneider and Flatau (Kong. f. 

 inn. Med., Berlin, June 11, 1897; Deutsch. med. Wchnschr., 1897, Vereinsbl. No. 18, 

 129; Fort. d. Med., 1897, 609) have noticed however, that changes in the anterior 

 horn ganglion cells of the spinal cords of rabbits are demonstrable two hours after 

 injection of tetanus toxin. 



