54 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



broth and divided into two parts, of which one is injected into 

 an animal just as it is, whilst the other is mixed with antitetanic 

 scrum and then injected. In a case of tetanus, the first animal 

 will die with tetanic symptoms, whilst the latter will survive 

 or die of sepsis without tetanus. 



BACILLUS PERFRINGENS. 



This bacillus, which appears in the literature under many different 

 names (B. aerogenes capsulatus, Welch's bacillus, etc., etc.), has 

 recently assumed great importance as the chief cause of "gas 

 gangrene." It was present in the majority of wounds seen in France 

 during the late war, and is not usually of serious import, requiring 

 special conditions before it causes gangrene. It is a large bacillus, 

 Gram-positive, having square or rounded ends, and is non-motile. 

 It has usually a very well-marked capsule, which is best demon- 

 strated by mixing a drop of the pus with indian-ink and spreading 

 the mixture out into a thin layer, which is allowed to dry (Burri's 

 method). The films may now be fixed and stained (best with watery 

 gentian violet) in the ordinary way, again dried and examined with 

 the oil-immersion lens. In successful specimens the large bacilli can 

 be seen to lie in clear spaces, surrounded by a dark background of 

 indian-ink. Spores are formed in the body, and in cultures in albumin- 

 ous materials, but not in glucose broth or other media containing sugar. 

 The organism produces a large amount of gas, which has an ex- 

 tremely evil odour. It is an anaerobe, but not a very strict one, and 

 can often be isolated in pure culture by adding a drop of pus contain- 

 ing the spores to a sterile milk-tube, boiling for a minute or two, 

 and incubating. The film of cream at the top will act as a seal 

 sufficient to exclude oxygen, and in twenty-four hours or less the milk 

 will be found to have divided inio a firm irregular mass of casein lying 

 in an acid whey containing enormous numbers of bacilli : gas bubbles 

 will probably be seen in this whey, especially if the tube is gently 

 shaken. 



No deductions can be drawn from its presence in wounds. 



BACILLUS (EDEMATIS MALIGNI. 



This organism (the Vibrion septique of Pasteur) is also frequently 

 found in war-wounds, but its r61e and its importance relatively to 

 B. perfringens are not accurately known. It is not unlike this latter 

 organism in appearance, and is Gram-positive, but this character is 

 readily lost in old cultures, or if the decolorization is pushed too far. 

 It forms spores. Usually rod-shaped, it often forms long chains or 

 filaments (especially in the dead bodies of animals), and these are 

 actively motile under anaerobic conditions (i.e., in the centre of a 

 preparation made by putting a drop of the culture or blood on a slide 

 and applying a cover-glass, but not round the edges). Like B. per- . 

 fringens, it gives off a large amount of gas which has an extremely 

 offensive odour. 



