434 



TETANUS 



may be impossible to isolate it from some cases of the disease, 

 but the cause of this very probably is the small numbers in 

 which it sometimes occurs. 



(a) The Disease as arising naturally. The disease occurs 

 naturally, chiefly in horses and in man. Other animals may, 

 however, be affected. In different animal species variations in 

 the clinical progress of the disease are observed. In man and in 

 the horse the spasms early affect the extensor muscles of the 

 trunk, while in other animals they may first appear in the 

 muscles neighbouring on the site of infection. There is in most 

 cases a definite wound, often of a ragged character, which has 



FIG. 129. Colonies of the tetanus bacillus on anaerobic 

 agar plates, seven days old. x 50. 



either been made by an object soiled with earth or dung, or 

 which has become contaminated with these substances. There 

 is often a purulent or foetid discharge, though this may be 

 absent. In tetanus following clean operation wounds, catgut 

 ligatures may be the source of infection. Microscopic examina- 

 tion of sections may show at the edges of the infected wound 

 necrosed tissue in which the tetanus bacilli may be very 

 numerous. If a scraping from the wound be examined micro- 

 scopically, bacilli resembling the tetanus bacillus may be 

 recognised. If these have spored, there can be practically no 

 doubt as to their identity, as the drumstick appearance which 

 the terminal spore gives to the bacillus is not common among 

 other bacilli. Care must be taken, however, to distinguish it 



