148 TETANUS, MALIGNANT (EDEMA, ETC. 



the end of that time cover-glass preparations are made 

 from the colonies along the streak or on the surface of the 

 agar plates. If some of the characteristic pin-shaped Ba- 

 cillus tetani are found, the cultures are treated as follows : 

 They are exposed from three-fourths to one hour to the 

 temperature of 80 C. ; in this way all the fully formed 

 bacteria and the greater part of the spores are killed, ihe 

 vegetative form of the Bacillus tetani included, but spores of 

 this bacillus remain alive. Then from these cultures fresh 

 gelatin, bouillon, or agar tubes are inoculated, and the same 

 grown at the temperature of the room or incubator in an 

 atmosphere of hydrogen. If the original substance experi- 

 mented with contained the Bacillus tetani, characteristic cult- 

 ures will be seen in this medium in a few days, and may 

 subsequently be transplanted. 



Motility and Thermal Death-Points. The Bacillus tetani in 

 the spore-bearing variety is non-motile ; the vegetative form is 

 quite motile, though no flagella have been discovered. A 

 temperature of 58 C. will destroy the non-spore-bearing 

 variety in a half-hour ; 60 C. will kill them in five 

 minutes ; and 65 C. instantaneously. Spores, however, are 

 able to resist a temperature of 80 C. for two hours, but are 

 killed by a temperature of 100 C. in from four to five min- 

 utes. When dried, the spores are capable of retaining their 

 vitality for months and years. Carbolic acid (5 per cent.) 

 will not kill them in less than ten hours ; but if 0.5 per 

 cent, hydrochloric acid be added to the carbolic acid solution, 

 spores will be destroyed in two hours. Bichloride of mer- 

 cury (1 in 1000) will destroy them in three hours. Bi- 

 chloride (1 in 1000) to which 6.5 per cent, hydrochloric acid 

 has been added will kill them in thirty minutes. 



Tetanin. The Bacillus tetani secretes a powerful poison, 

 known as tetanin, which diffuses in the cultures and is not 

 retained in the cell^body. 



The symptoms of tetanus are due to the action of this 

 toxin, and not to the influence of the bacteria themselves. 

 Tetanus is strictly a toxsemic disease. This is proved by the 

 fact that inoculations with cultures of bacilli in which the 



