36 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



123 



Tff~ 



out from the deep colonies also. Tliese tunnels with their curled ends are so striking and distinc- 

 tive that they form an infallible guide to the diagnosis of this bacillus. 



Agar slant. — Rapid growth takes place, and in twenty hours the surface is largely covered 

 with a very thin, translucent, faintly greenish layer, which has leafy margins. After several 

 days whitish specks, raised above the surface of the growth, appear, and the deposit in the water 

 at the bottom takes on a faint salmou color. 



Gelatin stab. — Growth occurs along the line of puncture, and by the third day a small funnel 

 of liquefaction has formed at top. The deposit is very dense looking and almost white, resem- 

 bling the pith of plants. After several days it begins to curl round at the bottom 

 in the way the tunnels from the colonies do. The walls of the funnel 

 often have au eroded lookj and little tunnels are sent out into the 

 gelatin, each one curling up at the end after a few days. The top of 

 the funnel is usually circular, but sometimes is eaten out into a very 

 irregular shape. The growth is very striking and characteristic. 



Potato. — Growth not visible until third day. when it has spread 

 widely over the surface in a very thin layer, moist and shining, about 

 the color of honey. After some time it becomes dryer looking, and 

 minute whitish dots appear in it. 



Bouillon. — Becomes diffusely cloudy in twenty-four hours. After 

 three weeks the growth has mostly settled to the bottom, leaving the 

 liquid tolerably clear. No skin forms on the surface. 



Rosolic acid. — Very slight growth. After five or six weeks the color is slightly deeper. 

 Litmus mill: — After six days becomes lighter but a purer blue. The color is discharged 

 entirely by the twelfth day. Reaction decidedly alkaline. No coagulation of the casein is 

 seen. 



Sugar gelatin, deep stab. — Growth quite deep, with liquefaction. Same appearance as in plain 

 gelatin. No gas production. 

 Indol. — Reaction negative. 



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

 Note. — In the report of the State board of health of Massachusetts for 1890, Jordan describes 

 a bacillus resembling the above in many respects under the name u Circulans."' He mentions also 

 having observed movement in the colonies of several other species, though not so marked or 

 constant. The bacillus Erodens differs in its action on milk and in its way of boring into the 

 gelatin. He speaks, though, of the funnel having a "ringed" appearance, which is seen in the 

 Erodens also. 



Bacillus Mesenteeicus Vtjlgattjs. 



Gel. stab. 



Bel. stab. 



Synonym: Potato bacillus (Fliigge). 

 (Figs. 32, 33, and 34, PI. III.) 



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



Character. — Strict aerobe; no development in atmosphere of hydrogen. 



Morphology. — Rather slender rods, straight, with rounded ends, from five to seven times as 

 long as broad. It occurs singly in short chains and in irregular groups, the rods lying side by 

 side. 



Spores are oval and formed near center of rod. At 35° to 36° C. spore formation is well 

 advanced in sixteen hours. The spores are usually large in proportion to size of rod, many of 

 them occupying two-thirds of the cell, and causing slight bulging of the walls. 



Motility. — Feebly motile. 



Flagella not demonstrated. 



Colonies on gelatin plates. — Colonies appear within twenty hours as minute whitish dots. 

 Those on the surface are almost without color, being faint bluish white, x SO. The deep colo- 

 nies appear as gray or brownish dots with regular margins, while near the edges fine lines can 

 be seen. The center is granular. On reaching the surface liquefaction goes on very rapidly, so 



