442 BACILLUS WELCHII 



produced by the b. welehii, infection of lacerated muscle has 

 been shown to be an extremely important factor in its origin 

 and spread {vide infra). 



This group of organisms may be said to have the following 

 characters. They are, on the whole, fairly large bacilli, easily 

 stained and Gram-positive, though the occurrence of Gram- 

 negative forms is fairly common in older cultures. Spore- 

 formation is the rule ; the spores, which are rounded or oval, 

 have a thickness exceeding that of the bacillus, sometimes 

 markedly' so, and may be terminal, subterminal, or central in 

 position. In a given species the position of the spore may vary 

 somewhat, but in the case of some, e.g., the b. tetani, the spore 

 is always terminal. The majority possess numerous lateral 

 flagella, and many are actively motile ; a few, e.g., the b. welehii, 

 are non-motile. The earlier means of differentiation depended 

 on morphological and cultural features in a few media, and on 

 pathogenic effects. All these factors, however, vary somewhat. 

 More recently the physical and chemical changes produced in 

 various definite media have been added as a means of distinguish- 

 ing them. The important work of M. Robertson, Henry, Wolf 

 and Harris, and M'Intosh may be mentioned in this connection, 

 and to their publications we are indebted for many of the facts 

 stated below. The appearances of superficial and deep colonies 

 have also been found of service. The result of biological inquiries 

 has been to divide the organisms according to their metabolic 

 activities into two main groups, namely, (1) the sacckarolytic or 

 non- proteolytic and (2) the proteolytic. This distinction must be 

 taken in a broad sense, as the proteolytic members have an action 

 on some sugars. Variations are met with in the rapidity of the 

 fermentation and also in the products which are ultimately 

 formed. The recognition of these two main groups is of 

 importance also from the pathological point of view, as the 

 chief organisms which produce spreading lesions belong to the 

 saccharolytic group. In fact there is often a " saccharolytic 

 stage " of advancing infection, followed, by a " proteolytic stage" 

 of putrefaction. We shall give the chief characters of the most 

 fully studied of these organisms, dealing first with the non- 

 proteolytic, which are the most important. 



Bacillus Welchu (B. Aekogenes Encapsulatus). 



This bacillus was first described by Welch and Nuttall in 

 1892, who showed that it was the cause of the extensive gaseous 

 development which sometimes occurs in the organs post mortem, 



