NON-PATHOGENIC BACILLI. 639 



mation occurs at the surface only, but after a time the entire medium is 

 colored red by the deposition of granular, colored masses from the surface 

 growth. Upon the surface of agar an abundant purplish-red layer is 

 formed, but the color is not absorbed by the culture medium. Upon potato 

 very rapid and abundant development occurs at the room temperature, 

 forming a thick, purplish-red layer which after some days has the color of 

 undissolved fuchsiii and a metallic lustre. Blood serum is liquefied by this 

 bacillus. In milk the development of Bacillus prodigiosus causes a precipi- 

 tation of the casein and a deep-red color of the medium. When cul- 

 tivated for some time in acid media the peptonizing (liquefying) power of the 

 bacillus is greatly reduced, as well as its chromogenic power. It has been 

 showji by Roger that animals which are not susceptible to the disease 

 known as malignant oedema, become infected and die when inoculated with 

 the malignant-oedema bacillus and at the same time with one or two cubic 

 centimetres of a culture of Bacillus prodigiosus. But this bacillus alone has 

 no decided pathogenic power. An interesting discovery made by Pawlowsky 

 is the fact that when rabbits are inoculated simultaneously with a virulent 

 culture of the anthrax bacillus and with a culture of Bacillus prodigiosus 

 they recover from the inoculation, the chemical products of one bacillus 

 having apparently the power to neutralize the toxic substances to which the 

 other owes its pathogenic potency. 



285. BACILLUS MESENTERICUS RUBER. 



Synonym. Rothen Kartoffelbacillus (G-lobig). 



Found upon potatoes. 



Morphology. Slender bacilli with round ends, united in pairs, in chains 

 of four, or in long filaments. 



Biological Characters. An aerobic, liquefying, motile, chromogenic 

 bacillus. Produces a reddish-yellow or pink pigment. Forms oval spores 

 which have a great resistance against high temperatures and germicidal 

 agents. Grows rapidly, especially at a temperature of 45 C. ; also at the 

 room temperature in the usual culture media. Upon gelatin plates, at 15 

 to 20 C., at the end of two days deep colonies are formed wnich are spheri- 

 cal and of a yellow color; when these come to the surface they spread out 

 as a fine network, around the margins of which projecting points are seen ; 

 liquefaction commences on the fom-th day and this network vanishes, leav- 

 ing a grayish-brown, friable mass at the bottom of the liquefied medium. In 

 gelatin stick cultures, at the end of three or four days, a cloudy white 

 growth is developed along the line of puncture, and liquefaction occurs in 

 funnel shape near the surface ; this soon exends to the walls of the tube and 

 downward, and a thin film is formed on the surface. Upon potato, at 

 15 C., at the end of three days the surface is covered by a thin, viscid, 

 slimy, yellowish, finely wrinkled layer; at 37 C. the entire surface is 

 covered in twenty-four hours with a reddish-yellow or pink layer; in forty- 

 eight hours this extends over the lower surface of the potato also, except 

 where it is in contact with the receptacle in which it is placed. 



286. BACILLUS PYOCYANUS ft (Ernst). 



Found in pus from bandages colored green. 



Morphology. Slender bacilli from 2 to 4 u long occasionally 5 to 6 // 

 and from 0.5 to 0.75 n broad; sometimes united in pairs, or chains of three 

 elements. 



Biological Characters. An aerobic, liquefying, actively motile, chromo- 

 genic bacillus. Produces a yellowish-green pigment; when old cultures 

 are shaken up with chloroform and this is allowed to stand, three layers are 

 formed an upper, clouded, dirty-yellow layer; below this is a milky, pale- 

 green layer; and at the bottom a transparent, azure-blue layer. Spore for- 

 mation has not been demonstrated. Grows in the usual culture media at the 



