■MORPHOLOGY AND PATHOGENESIS. 403 



Morphology. — The bacillus resembles somewhat B. anthracis, 

 but generally is stouter and more variable in length (Fig. 136), 

 on an average 3-6 /ti, but it may be found in pairs so short as to 

 resemble diplococci, or so long as to form filaments, and chains 

 of 4 to 30 units may be met with. The ends of free bacilli are 

 obtusely rounded, whilst those of organisms in a chain are square 

 cut. The bacillus is usually possessed of a capsule, especially 

 when found in body fluids, rarely 

 in artificial media, but at all times 

 the capsule stains with difficulty. 



Spores are generally to be 

 found in blood-serum cultures 

 after four days' incubation, and 

 occasionally they have been ob- 

 served in cultures in all of the 

 common media. It would ap- 

 pear, however, that some races 

 are devoid of the power to form 



spores. • The majority of the fig. 136. — Bacillus aerogenes capsu- 



Spores are oval in form, less fre- '^t"=- -Showing one large encapsuled 



^ ' form. The others in the field are of the 



quently round, and may be situ- same species, but smaller. (Dr. Charles 



ated in the cell either centrally, "' ^°""-' "" '°°°- 

 towards one end, or at the end, and are usually of slightly greater 

 diameter than the bacillus itself. Two have never been found 

 in one cell. They stain readily by any of the ordinary spore- 

 staining methods. They withstand the temperature of boiling 

 water for six minutes, but are killed by eight minutes' boiling. 

 The vegetative cells, however, perish by an exposure of ten 

 minutes in moist heat at 58° C. The bacilli are not possessed 

 of flagella and are non-motile. They stain by Gram's method. 

 Pathogenesis. — In man, as pointed out by Fraenkel, Welch, 

 Bloodgood, and others, this bacillus is the most frequent cause 

 of emphysematous gangrene. It has been repeatedly found in 

 the inflammatory subcutaneous emphysema following upon in- 

 jections of salt solution, due to imperfect sterilisation of the 

 instrument or fluid. It has been cultivated from the blood dur- 

 ing life in two cases at least — by Gwyn in a case of acute cho- 

 rea which ended fatally, and by Cole, recently, in the Johns 

 Hopkins Hospital, from the blood of a man whose leg had been 

 crushed in a railroad accident and was at the time of culture 



