mi-: DIPLOCOCCU8 <>!' r\i-:r.Mn\i.\ 



human or ani i al blood serum or ascitic or pleuritic fluid and two- 

 thirds bouillon or nutrient agar growth in milk. 



GROWTH IN M U.K. It grows readily in milk, causing coagulation 

 with the production of acid, though this is not constant with some 

 forms intermediate between the streptococcus and pneumococcus. 



GROWTH ox AGAR. Cultivated on plain nutrient agar, after twenty- 

 four to forty-eight hours at 37 C., the deep colonies are hardly visible 

 to the eye. Under the microscope they appear light yellow or brown 

 in color and finely granular. The surface colonies are large, equalling 

 in size those of streptococci, but are usually more transparent. If blood 

 serum or ascitic fluid be added to the agar the individual colonies are 

 larger and closer together, and the growth is more distinct in conse- 

 quence and of a grayish color. The surface colonies are almost circular 

 in shape under a magnification of 60 diameters, finely granular in struc- 

 ture, and may have a somewhat darker, more compact centre, surrounded 

 by a paler marginal zone. With high magnification cocci in twos and 

 short rows often distinctly separated are seen at the edges. In stick 

 cultures minute transparent drops appear along the line of puncture. 



GROWTH ox GELATIX. The growth on gelatin is slow, if there is 

 any development at all, owing to the low temperature viz., 24 to 

 27 C. above which even the most heat-resistant gelatin will melt. 

 The gelatin is not liquefied. 



GROWTH ox BLOOD SERUM. The growth on Loeffler's blood-serum 

 mixture is very similar to that on agar, but somewhat more vigorous 

 and characteristic, appearing on the surface as a delicate layer of dew- 

 like drops. 



GROWTH IN BOUILLON. In bouillon, at the end of twelve to twenty- 

 four hours in the incubator, a slight cloudiness of the liquid will be 

 found to have been produced, due to the development of the micrococci. 

 On microscopic examination these can be seen to be arranged in pairs 

 or longer or shorter chains. In two or three days the medium again 

 becomes transparent owing to the subsidence of the cocci. After one 

 or two transplantations the pneumococci frequently fail to grow. 



SPECIAL MEDIA. Fraenkel was the first to draw attention to the 

 fact that this organism soon loses its reproductive power when grown 

 on ordinary culture media, and more particularly solid media. In fluid 

 media the vitality is not quite so quickly lost; but even here it is found 

 advisable to transplant fresh cultures every day. When cultures are 

 grown on serum-free media the vitality of some cultures may indeed 

 be indefinitely prolonged; but after transplantation through several 

 generations it is found that the cultures begin to lose in virulence, 

 and that they finally become non-virulent. In order to restore this 

 virulence, or to keep it from becoming attenuated, it is necessary to 

 interrupt the transplantation and pass the organism through the bodies 

 of susceptible animals. 



With the view of overcoming these obstacles in the way of culti- 

 vating this rnicrococcus, several special media have been proposed by 

 various experimenters in the place of the ordinary culture media. The 



