1 70 SUPPURATION AND ALLIED CONDITIONS. 



Cultures on agar kept at the body temperature may 

 often be found to be dead after ten days. On potato, 

 as a rule, no visible growth takes place. In bouillon, 

 growth forms numerous minute granules which after- 

 wards fall to the bottom, the deposit, which is usually 

 not very abundant, having a sandy appearance. The 

 appearance in broth, however, presents variations which 

 have been used as an aid to distinguish different species of 

 streptococci. It has been found that those which form the 

 longest chains grow most distinctly in the form of spherical 

 granules, those forming short chains giving rise to a finer 

 deposit. To a variety which forms distinct spherules of 

 minute size the term streptococcus conglomeratus has been 

 given. The question as to the existence of varieties of 

 streptococcus pyogenes will be discussed below. 



Bacillus Coli Communis. The microscopic and cultural characters 

 are described in the chapter on typhoid fever. The bacilhis lactis 

 cerogenes and the bacillus pyogenes fatidits closely resemble it ; they are 

 either varieties or closely related species. The former is distinguished 

 by producing more abundant gas formation, and by its growth on 

 gelatine, etc., being thicker and whiter than that of the bacillus coli. 



Bacillus Pyocyaneus. This organism occurs in the form of minute 

 rods 1.5 to 2 fj- in length and less than . 5 /* in thickness. Occasion- 

 ally two or three are found attached end to end. They are actively 

 motile, and do not form spores. They stain readily with the ordinary 

 basic stains, but are decolorised by Gram's method. 



Cultivation. It grows readily on all the ordinary media at the 

 room temperature, the cultures being distinguished by the formation 

 of a greenish pigment. In puncture cultures in peptone-gelatine a 

 greyish line appears in twenty-four hours, and at its upper part a 

 small cup of liquefaction forms within forty-eight hours. At this time 

 a slightly greenish tint is seen in the superficial part of the gelatine. 

 The liquefaction extends pretty rapidly, the fluid portion being turbid 

 and showing masses of growth at its lower part. The green colour 

 becomes more and more marked and diffuses through the gelatine. 

 Ultimately liquefaction reaches the wall of the tube. In plate cultures 

 the colonies appear as minute whitish points, those in the surface being 

 the larger. Under a low power of the microscope they have a 

 brownish-yellow colour and show a nodulated surface, the superficial 

 colonies being thinner and larger. Liquefaction soon occurs, the 

 colonies on the surface forming shallow cups with small irregular 

 masses of growth at the bottom, the deep colonies small spheres of 



