1 68 BACTERIA 



ing their nidus in ordinary soil. The three chief members 

 of this group are the bacillus of Tetanus (lockjaw), the 

 bacillus of Quarter Evil, and the bacillus of Malignant 

 CEdema. 



Tetanus. The pathology of this terrible disease has 

 during recent years been considerably elucidated. It was 

 the custom to look upon it as " spontaneous," and arising 

 no one knew how ; now, however, after the experiments of 

 Sternberg and Nicolaier, the disease is known to be due to 

 a micro-organism common in the soil of certain localities, 

 existing there either as a bacillus or in a resting stage of 

 spores. Fortunately Tetanus is comparatively rare, and 

 one of the peculiar biological characteristics of the bacillus is 

 that it grows only in the absence of oxygen. This fact con- 

 tributed not a little to the difficulties which were met with 

 in securing its isolation. 



Tetanus occurs in man and horses most commonly, though 

 it may affect other animals. There is usually a wound, 

 often an insignificant one, which may occur in any part of 

 the body. The popular idea that a severe cut between the 

 thumb and the index finger leads to tetanus is without 

 scientific foundation. As a matter of fact, the wound is 

 nearly always on one or other of the limbs, and is infected 

 simply because they come more into contact with soil and 

 dust than does the trunk. It is not the locality of the 

 wound nor its size that affects the disease. A cut with a 

 dirty knife, a gash in the foot from the prong of a gardener's 

 fork, the bite of an insect, or even the prick of a thorn have 

 before now set up tetanus. Wounds which are jagged, and 

 occurring in absorptive tissues, are those most fitted to allow 

 the entrance of the bacillus. The wound forms a local man- 

 ufactory, so to speak, of the bacillus and its secreted poisons ; 

 the bacillus always remains in the wound, but the toxins may 

 pass throughout the body, and are especially absorbed by 

 the cells of the central nervous system, and thus give rise 



