MODE OF INFECTION 1 87 



The tetanus bacillus is very resistant, especially in its 

 spore form, to destructive agents such as drying and the or- 

 dinary disinfectants. Kitasato found that a 5 per cent sol utio n_ 

 of carbolic acid applied for ten hours failed to kill the spores^, , 

 Tizzoni and Cattani found that mineral and organic acids pro- 

 duced no effect upon the dried spores. Behring found that 

 iodine trichloride possesses a strong antiseptic effect upon them. 

 They are not affected by the gastric fluids. It has been noted 

 by Kitt that the dried spores in pus have retained their viru- 

 lence for sixteen months. They are destroyed when subjected 

 to a temperature of 100° C. in water or steam for ten minutes. 

 The bacilli in the vegetative state are readily destroyed by the 

 usual strong disinfectants, such as 5 per cent carbolic acid. 



A number of pseudo-tetanus bacilli have been described. 

 This renders a careful study of the suspected organism neces- 

 sary as it is difficult in some cases to determine microscopically 

 B. tetani. The guinea pig inoculation affords a ready m.eans 

 of differentiation whenever fresh material is available. 



§ 145. Mode of infection. As the bacillus of tetanus 

 is widely distributed in the soil and consequently on articles 

 contaminated with it, the most common modes of infection are 

 punctures scratches, and pricks made by splinters, nails or 

 infected instruments (traumatic tetanus). It maj' follow 

 slight abrasions of the skin where infected earth comes in con- 

 tact with the lacerated epidermis. Infection through wounds 

 in the intestinal mucosa do not seem to have been clearly 

 demonstrated. The most usual method seems to be by pricks 

 and nail punctures, in which cases the virus can be carried 

 well into the living tissues and there is little or no bleeding to 

 wash it out. 



Infection often occurs in young foals and lambs through 

 the freshly broken umbilical cord (tetanus neonatorum). 

 The symptoms begin to appear in a variable length of time 

 after the infection takes place. The shortest period which 

 seems to be reported is a few hours and the longest is six 

 weeks. In horses the period of incubation is usually from 

 four to twenty days. After inoculation with pure cultures it 

 is from four to five days and in sheep from two to four days. 



