C32 NOX-PATHOGENIC BACILLI. 



violet color is not developed, but when nitrates are added the growth is more 

 luxuriant and a rich violet color is produced. Nitrates are reduced to- ni- 

 trites by this bacillus, rather slowly. 



269. BACILLUS TREMELLOIDES (Schottelius). 



Found in the Freiburg water supply by Tils. 



Morphology. Bacilli with round ends, from 0.75 to 1 n long and 0.25 n 

 broad, associated in friable masses. 



Biological Characters. An aerobic, liquefying, chromoqenic bacillus. 

 Forms a golden -yellow pigment. Spore formation not observed. Grows in 

 the usual culture media at the room temperature. Upon gelatin plates the 

 deep colonies appear as yellow points ; at the end of forty-eight nours the 

 superficial colonies appear as prominent yellow masses and the plate looks 

 as if it were covered with coarse sand ; at the end of a few days the colonies 

 measure several millimetres in diameter and do not subsequently increase 

 in size ; under a low power these are seen o be made up of cloud-like masses 

 and have a yellow or yellowish-brown color, the contour is smooth or irre- 

 gularly bulging; at the end of eight days the margin is surrounded by a 

 golden-yellow, slimy layer and the colony commences slowly to sink into 

 the gelatin. In gelatin stick cultures isolated, punctiform, yellow colonies 

 are developed along the line of inoculation, and upon the surface a colony 

 which resembles those upon gelatin plates ; at the end often to fourteen days 

 the superficial layer is slowly depressed as a result of liquefaction of the 

 underlying gelatin. Upon the surface of agar a layer is developed which 

 is at first dry and granular, later slimy and of a golden-yellow color. Upon 

 potato a yellow layer is developed which may attain a thickness of several 

 millimetres; after a long time the growth is surrounded by a golden-yellow, 

 slimy zone, and no further extension occurs upon the surface of the potato. 

 In milk, at the end of thirty-six hours, a strongly acid reaction is produced 

 and the fluid becomes viscid. 



270. BACILLUS CUTICULARIS (Tils). 



Found in water. 



Morphology. Bacilli from 2 to 3 n long and 0.3 to 0.5/f broad; may 

 grow out into short filaments. 



Biological Characters. An aerobic, liquefying, motile, chromogenic 

 bacillus. Spore formation not observed. Forms a yellow pigment. The 

 shorter rods are slightly motile, the longer filaments not. Grows in the 

 usual culture media at the room temperature. Upon gelatin plates the deep 

 colonies appear under the microscope as brownish discs with an irregular 

 but smooth contour. The superficial colonies are yellowish-brown in color, 

 with well-defined contour; after several days the centre commences to be 

 depressed and the gelatin is quickly liquefied ; the colony then consists of a 

 membranous film surrounded by a well-defined zone of liquefied gelatin; 

 finally the gelatin of the plate is entirely liquefied and these membranous 

 colonies float upon the surface. In gelatin stick cultures, at the end of two 

 days, liquefaction commences near the surface and progresses rapidly; a 

 membranous layer is formed on the surface. Upon potato development is 

 slow, in the form of a pale-yellow layer, which later becomes slimy and 

 dark-yellow. In milk a pale-yellow, membranous layer is formed upon the 

 surface in from twenty-four to thirty-six hours, and an odor of sulphuretted 

 hydrogen is developed. 



271. FLESH-COLORED BACILLUS (Tils). 



Found in water. 



Morphology. Bacilli of 2 j* in length and 0.5 t* broad ; in hanging-drop 

 cultures always seen solitary and in active motion. 



