190 CLASSIFICATION OF THE MICRO-ORGANISMS. 



In puncture 

 cultivations. 



In stroke 

 cultivations. 



Effect on 

 animals. 



small, slightly prominent transparent drops, about J mm. 

 in diameter. Even after several days there is no 

 extension of these colonies and no liquefaction of the 

 gelatine. Under a low power the youngest colonies 

 present the appearance of round, seldom oval, yellow 

 spots, with regular contours and finely granular surface. 

 Later they become somewhat darker, almost brown, 

 and the border is here and there interrupted by pro- 

 jecting chains of cocci, which either terminate in a 

 free end, or form loops ; the growth is somewhat more 

 marked on agar plates, the colonies are rather broader 

 and opaque. Along the track of the puncture in 

 gelatine a delicate layer appears, which consists, either 

 entirely or in part, of isolated colonies ; these are of a 

 faintly whitish appearance, almost transparent, very small; 

 only a few attain the size of a pin's head. In stroke culti- 

 vations the streptococcus seldom forms continuous lines, 

 it usually occurs in discrete centres ; on agar the growth 

 is thickest in the middle, and becomes gradually thinner 

 in a terrace-like form towards the periphery ; at the peri - 

 phery punctiform masses of the organisms can be seen here 

 and there. On solidified blood serum the growth is similar 

 to that on agar; it does not seem to grow on potatoes. 



In mice in the majority of cases (about 80 per cent.) 

 no effect follows the subcutaneous inoculation of small 

 quantities ; at times slight suppuration occurs at the 

 point of inoculation, at times the animals die without 

 the presence of any marked pathological change or of 

 micro-organisms in any of the organs. If rabbits arc 

 inoculated on the ears marked redness and swelling 

 occurs on the following day, but disappears on the 

 second or third days ; subcutaneous and even intra- 

 venous injection of considerable numbers of the strepto- 

 cocci cause as a rule no apparent effect in healthy rabbits. 

 It is only when the animals are artificially weakened, as 

 for example by the injection of toxic substances, that death 

 occurs from marked growth of the micrococci; the animals 

 also died after 2 5 days from extensive endocarditis, with 

 numerous deposits of streptococci, if the aortic valves 

 had been injured before the injection (Wysokowitsch). 



