MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 35 



Gelatin stab. — By the end of twenty-four hours a saucer of liquefaction 3 mm. in diameter lias 

 formed, and growth is seen deep down the puncture. By uext day the liquefaction has nearly 

 reached the tube wall, but is shallow, and a pellicle has formed on the surface, which soon becomes 

 wrinkled, and climbs up the tube wall 2 to 3 mm. The liquefaction becomes funnel shaped by the 

 fourth day and by the tenth is almost complete. The growth settles to the bottom in whitish 

 Bakes, leaving the liquid clear, but few tiocculi floating in it. 



rotnto. — A dry-looking white growth soon covers a large part of the surface, and by the third 

 day is thrown into large folds. These soften dowu after some days, and at the end of two weeks 

 the growth is a putty colored, moist, slimy looking layer. It is not tenacious, however, and does 

 not cling to the needle. 



Bouillon. — Becomes diffusely cloudy, a uiyeoderma/orms on the surface in four or five days, 

 and the bottom of the tube is covered with a dense whitish deposit, while cotton-like tiocculi float 

 in the liquid. 



Rosolic acid. — No growth. 



Litmus mill:. — Reddish tint is seen about the third day, and coagulation in tiocculi takes place 

 in four to five days. The color is rapidly discharged and the casein is dissolved by the end of ten 

 days. A white mass floats on the surface, and there is a whitish deposit at the bottom. The 

 reaction is alkaline at end of two weeks. 



Sugar gelatin, deep stab. — Good growth deep down, with rapid liquefaction. No gas produced. 



Indol. — Faint color is produced by the addition of both sulphuric acid and sodium nitrite. 

 It does not come at once. 



Relation to temperature. — More rapid growth at 35° to 36° C. 



Note. — This bacillus is much like the potato bacillus, and belongs to that group without 

 doubt. The chief points of difference are its effect on milk, the appearance of the deep colonies, 

 and the production of indol. 



Bacillus Eeodens. 



(Fig. 31, PI. III.) 



Found at the depth of 6 feet in made soil, which had been paved for a number of years. 



(.7i«>-«cte>\— Requires oxygen for good development, though it shows some growth in an 

 atmosphere of hydrogen. 



Morphology. — Straight, thick rods, with rounded ends, from three to seven times as long as 

 broad. Occurs singly for the most part. 



Spores are formed rapidly at incubator temperature, the process being well advanced in 

 sixteen hours. They are oval and formed near the center of the rods, often causing bulging of 

 the wall of the cell. After a time the rods seem to shorten around the spore, and separated 

 spores have not been demonstrated. 



Moti I i ty. — Actively motile. 



Flagella not demonstrated. 



Colonies on gelatin plates. — Colonies are seen in twenty to twenty-four hours as minute whitish 

 dots, x 80. Some resemble a small raspberry, while others show more of a nest-like arrangement, 

 the granules not being so well marked. At the end of thirty-six hours the colonies are about 

 one-tenth of a millimeter in diameter, and look white. xSO. They are round, with even edges, 

 and dark gray in color. The distinctive feature about them is the movement of the contents, 

 which is active and incessant. It is usually in the general direction of the hands of a watch, 

 with many smaller eddies. On the third day the surface colonies may be 2 mm. in diameter, 

 have well defined edges, and look as if they had been punched out. The even contour is usually 

 kept at the surface, while the growth eats away the gelatin below. In some the action is uniform 

 all around, so that the opening at the surface may be 2 mm. in diameter, while at the bottom 

 it is 3 or 4 mm. The most constant feature, however, is the putting out of tunnels from 

 the sides of the colony, some colonies having as many as five radiating from them. These extend 

 2 or 3 mm. and tend to curl up near the ends. A scant whitish growth is seen on the floor 

 of each. The active movement in the colonies stops about the third day, probably from drying 

 up, but is seen in the ends of these tunnels for five or six days. Occasionally a tunnel is sent 



