462 BACTERIOLOGY. 
growing readily at a temperature from 18° to 20° C., 
but best at 37°, in milk, bouillon, and other liquid 
media, and in nutrient gelatin or agar, accompanied by 
liquefaction of the gelatin. 
Growth on Gelatin. Grown on gelatin plates it 
develops, at room-temperature within forty-eight hours, 
punctiform colonies, which, when examined under a 
low-power lens, appear as circular disks of a pale brown 
color, somewhat darker in the centre, and surrounded 
by a smooth border. The colonies grow rapidly. The 
Fic. 59. 
Staphylococcus.  < 1100 diameters. 
appearance of the growth is most characteristic. Im- 
mediately surrounding the colonies, which are of a pale 
yellow color, there is a deepening of the surface of the 
gelatin, due to its liquefaction. By suitable light a 
number of these shallow depressions with sharply de- 
fined outlines may be seen on the gelatin plate, having 
a diameter of from 5 to 10 mm., in the centres of which 
lie the yellow colonies. Later, the liquefaction becomes 
general, the colonies running together. In stick cul- 
tures in gelatin a white confluent growth at first appears 
