478 PATHOGENIC AEROBIC BACILLI 



ing, motile bacillus. Forms endogenous spores. Grows readily in the usual 

 culture media at the room temperature. 



In gelatin plates small, round or oval colonies are formed, which later 

 become pear-shaped ; a branching outgrowth occurs about the margins of the 

 colonies, and especially from the small end of the pear-shaped mass. In 

 streak cultures upon the surface of gelatin growth occurs first along the impf- 

 strich, and from this an outgrowth occurs consisting of bacilli in a single 

 row or in several parallel rows, and forming irregular or circular figures, 

 from which other similar outgrowths occur; the branching outgrowths may 

 anastomose. The gelatin is liquefied in the vicinity of these lines of growth, 

 forming a network of channels. A similar growth is seen upon the surface 

 of gelatin stick cultures, and along the line of puncture white, irregular 

 masses are formed, from which rather coarse branches are given off which 

 often have a club-shaped extremity. In older cultures the finer branches 

 disappear, so that the secondary centres of growth are disconnected from the 

 original colonies ; complete liquefaction of the gelatin occurs in about two 

 weeks ; the liquefied gelatin has a yellowish color and peculiar odor. Upon 

 the surface of nutrient agar, at 37 C., a white layer is formed. Upon potato 

 the development is slow and results in the formation of a dry, yellowish 

 layer. In milk coagulation first occurs, and the coagulum is subsequently 

 dissolved; a slightly acid reaction is produced. This bacillus grows best in 

 the incubating oven at 37, and does not develop at temperatures below 16 3 

 C. The spores require for their destruction a temperature of 100 C. main- 

 tained for four minutes (determined by the writer, 1887). 



Pathogenesis. The introduction of pure cultures of this bacillus into 

 hives occupied by healthy swarms causes them to become infected with foul 

 brood ; grown bees also become infected when given food containing the ba- 

 cillus (Cheshire). Mice injected subcutaneously with a considerable quan- 

 tity die within twenty-four hours, guinea-pigs in six days (Eisenberg). 

 Small amounts injectea beneath the skin of mice or rabbits produce no appa- 

 rent result. 



141. BACILLUS OF ACNE CONTAGIOSA OF HORSES. 



Obtained by Dieckerhoff and Grawitz (1885) from pus and dried scales 

 from the pustules of ' ' acne contagiosa " of horses. 



Morphology. Short rods, straight or slightly bent, 0.2 jj. in diameter. 



Stains best with an aqueous solution of fuchsin, and also by Gram's 

 method ; does not stain well with Loffler's alkaline solution of methylene 

 blue. 



Biological Characters. An aerobic, non-liquefying bacillus. In gelatin 

 stick cultures a very scantv growth occurs along the line of puncture ; upon 

 the surface a white mass forms about the point of puncture. Upon blbod 

 serum and nutrient agar an abundant growth at the end of twenty-four 

 hours at 37 C., consisting of white colonies along the impfstrich, which 

 later have a yellowish-gray color. The growth is more abundant and rapid 

 upon blood serum than upon other media. 



Pathogenesis. Pure cultures of the bacillus described are said by Diecker- 

 hoff and Grawitz to produce typical acne pustules when rubbed into the skin 

 of horses, calves, sheep, and dogs. When rubbed into the intact skin of 

 guinea-pigs a phlegmonous erysipelatous inflammation was produced, and 

 the animal died at the end of forty -eight hours with symptoms of toxaemia. 

 Subcutaneous injections in guinea-pigs caused toxaemia and death at theend 

 of twenty-four hours. At the autopsy a haemorrhagic infiltration of the in- 

 testinal mucous membrane was observed ; the bacilli were not found in the 

 internal organs. In rabbits pure cultures rubbed into the intact skin caused 

 a development of pustules and a severe inflammation of the subcutaneous 

 connective tissue, from which the animal usually recovered. Subcutaneous 

 injections in rabbits sometimes caused a fatal toxtemia. House mice, field 

 mice, and white mice were not affected by the application of cultures, by 



