﻿484 MTJSGRAVE AND CLEGG. 



but a slower development takes place even at ordinary room temperature 

 (30° C). The organism is an obligate aerobe. 



Potato. — Growth becomes visible after twenty-four hours and after seventy- 

 two becomes luxuriant. The colonies, when they first become apparent, are small, 

 discrete and slightly raised, and have a delicate, pink color. As growth proceeds 

 they become larger at the base and raised to a height of at least 0.1 millimeter. 

 The upper portion of the colony appears as a short shred which often folds upon 

 itself, giving it the appearance of being umbilicated. The whole inoculated surface 

 finally changes to a heaped-up mass which has a yellow-ocher color in the 

 center, with a pinkish or white periphery. The medium becomes darkened and 

 moist. The growth may be lifted in heaps on a platinum loop. Desegmentation 

 occurs when it is placed in water and small, flat particles, from delicate pink 

 to a yellowish-brown color and which resemble dry bran, float upon the surface; 

 on shaking the vessel the particles adhere to the sides of the vessel. (PI. IV, 

 fig- 2.) 



Glycerin agar. — Growth appears after three days; later it becomes heaped up, 

 the medium remaining moist. The colonies at first are discrete, but they soon 

 become confluent, but not diffuse ; they are raised and in some instances have 

 the umbilicated appearance observed on potato. As the cultures grow older, 

 they to some extent resemble those of the tubercle bacillus on the same medium. 

 A yellowish pigment is produced, more pronounced in the central portion where 

 the growth is more luxuriant ; with a pink to pinkish-white periphery. The 

 growth may readily be peeled from the surface of the medium, and when observed 

 in bulk it has a moist appearance. No pigmentation of the medium occurs. 

 (PI. IV, fig. 1.) 



Agar-agar 1 per cent acid and 1 per cent alkaline to phenolphthalein. — The 

 growth after four days' incubation appears as a smooth, white and glistening, 

 very slightly raised mass. The colonies do not develop the central pit, thus 

 differing from their appearance on potato, glycerin agar and the media containing 

 sugar, neither do they produce the pigment which is characteristic of growth 

 on the latter, but on the contrary they first assume a porcelain-white color and 

 later develop a delicate, diffuse pink. There is no pigmentation of the medium. 



Loeffler's blood serum. — Growth on this is much slower than on other media. 

 The pigmentation and growth are very similar to those on plain agar-agar. After 

 two weeks' incubation no change in the medium occurs. 



Glucose agar stab. — Colonies do not develop along the track of the needle, but 

 they grow luxuriantly on the surface of the medium forming a heaped-up center, 

 with a wrinkled periphery. The center is yellow in color, the periphery pink 

 to pinkish-white. No pigmentation of the medium occurs. The growth on this 

 medium shows the aerobic tendencies of the microorganism. 



Gelatin. — This medium is not liquefied; growth is similar to that on glucose 

 agar. 



Bouillon, alkaline and acid. — Floating, flat particles appear on the surface of 

 the medium after three days' incubation. These particles, when the tube is 

 shaken, adhere to its sides. On further incubation, a sediment in the form of 

 a tenacious mass settles to the bottom. The medium does not become cloudy, but 

 on long incubation it changes to a darker color. 



Alkaline litmus-milk. — Growth appears after three days on the surface of 

 the medium in the form of dry, flat particles, which later become confluent, form- 

 ing a heaped-up, yellowish mass. A tenacious sediment forms at the bottom 

 of the tube ; in this portion of the medium the milk is gradually decolorized ; 

 however, it does not become red. The milk is not coagulated. 



