

MORPHOLOGY 285 



in groups. In broth cultures it forms short chains (fig. 182). The bacilli 

 are more numerous in the spleen and lymphatic glands than in the blood. 

 They are frequently found within the leucocytes, and in sections masses 

 of bacilli will be seen within the capillaries. 



The bacillus is not known to form spores. 



Staining methods. The bacillus of swine erysipelas stains readily with 



FIG. 182. Bacillus of swine erysipelas (broth FIG. 183. Bacillus of swine erysipelas in 



culture). Carbol-thionin. (Oc. iv, obj. T ^th, pigeon's blood Gram's stain. (Oc. iii, obi. 



Reichert.) Ath, Reichert.) 



the basic aniline dyes, is gram-positive, and retains the violet in Claudius' 

 method. The best methods to use are : 



(a) Cultures. Stain with carbol-thionin or dilute carbol-fuchsin. 



(6) Blood-films and smears of tissues. Carbol-thionin or carbol-methylene- 

 blue may be used, but Gram's method is preferable. 



(c) Sections. Gram's method should be used with either double or triple 

 staining (p. 219). 



2. Cultural characteristics. 



Conditions of growth. The bacillus of swine erysipelas 

 is indifferently aerobic. Growth is better under anaerobic 

 conditions but is always rather scanty. 



Cultures, which should be sown with the blood, pulp of 

 organs, or bone marrow of an animal recently dead of the 

 disease, are easily obtained at temperatures between 15 

 and 40 C. on the ordinary media. 



Broth. The medium soon becomes slightly opalescent 

 when incubated at 33-38 C. The growth which is always 

 scanty ceases about the fourth day, and subsequently forms 

 a very small white precipitate. 



Gelatin. Stab culture. The growth in gelatin stab-culture 

 is characteristic. Along the stab a thin opaque line de- 

 velops, from which numerous small very delicate branching 

 filaments radiate. The growth is more luxuriant in the depth 

 of the stab. Towards the twentieth day, the characteristic 

 appearance vanishes and the culture becomes cloudy. There 

 is never any liquefaction of the gelatin (fig. 184). 



Stroke culture. Cultures on the surface of a sloped O f swine erysipelas, 

 gelatin tube radiate from the line of sowing like the feathers gfJg'JjUS? in gela " 

 of a quill. 



Single colonies. Fine downy flocculi giving off delicate radiating fila- 

 ments are seen embedded in the gelatin, then the appearance becomes 



