084 NON-PATHOGENIC BACILLI. 



395. LEPTOTHRIX BUCCALIS OF VIGNAL. 



Found by Vignal in the healthy human mouth rare. Supposed by 

 Vignal to be identical with Leptothrix buccalis of Robin ; but as the charac- 

 ters of the microorganism receiving this name were not definitely deter- 

 mined by Robin, such identification is impossible. It seems more probable 

 that the large bacillus described by Miller (Bacillus buccalis maximus), 

 which is found very commonly in the human mouth, but has not been cul- 

 tivated, is the leptothrix of Robin. 



Morphology. Bacilli from 1 to 1.5 IJL in breadth and varying greatly in 

 length from 1.6 to BO M; often united in long chains, or in filaments which 

 are seen to be segmented when treated with staining, agents. This lepto- 

 thrix is characterized by the presence of transverse partitions in the interior 

 of the rods, seen only in stained preparations ; these are best seen in old 

 rods, which are less deeply stained than those of more recent development; 

 the partitions in these are more deeply stained than the remaining portion 

 of the filament. 



Biological Characters. An aerobic, liquefying bacillus. Spore forma- 

 tion not observed. Grows very slowly in the usual culture media at tempe- 

 ratures above 20 C. Upon gelatin plates, by the third or fourth day, small, 

 round, grayish-white, projecting colonies are formed ; by the fifth or sixth 

 day an irregular border of rounded festoons is developed; this is semi-trans- 

 parent and presents depressions and ridges which are radial or parallel 

 with the margin; the prominent centre remains opaque and of a grayish- 

 white color; later this border extends considerably and the gelatin below it 

 becomes liquefied. In gelatin stick cultures, at the end of forty-eight 

 hours, a small mass is developed at the point of puncture, about two milli- 

 metres in diameter, and a slender line of growth is visible along the track of 

 the needle below ; by the fourth day the surface growth has a diameter of five 

 to six millimetres, and below it a little transparent, liquefied gelatin is seen in 

 a cup-shaped cavity ; this increases slowly in dimensions and the liquefied gela- 

 tin remains clear, while a bluish mycoderma is seen upon the surface; the 

 growth along the line of puncture remains scanty, but is a little more abun- 

 dant above in contact with the cup shaped cavity; by the eighth day this ex- 

 tends to the walls of the tube; by the twelfth day the cup form has disap- 

 peared and the gelatin is liquefied to a depth of about one centimetre ; it is 

 still covered with a bluish membranous layer, and a scanty whitish deposit 

 of leptothrix filaments is seen at the bottom of the liquefied gelatin Upon 

 the surface of agar, at the end of twenty-four hours at 36 to 38 C., a 

 slightly wrinkled, transparent, white layer is developed; later this is still 

 more wrinkled, dry, and of a transparent yellow color; it is easily broken 

 up. In neutral bouillon a slight cloudiness is produced and a scanty white 

 precipitate is formed at the bottom of the tube; no mycoderma develops upon 

 the surface. Upon potato a layer is developed which is of a dirty-white 

 color at the centre and of a purer white near the margins. 



396. BACILLUS b OF VIGNAL. 



Obtained quite frequently by Vignal in cultures from healthy buccal se- 

 cretions. 



Morphology. Bacilli with square ends, straight or slightly curved, about 

 0.5 n in diameter and varying greatly in length from 1.5 to6.5//; often 

 united in chains. 



Biological Characters. An aerobic, liquefying bacillus. Spore forma- 

 tion not observed. Motility not mentioned. Grows rather slowly at the 

 room temperature more abundantly at 37 C. Upon gelatin plates, at the 

 end of twenty-four hours at a temperature of 18' to 20 C., prominent, 

 small, grayish-white colonies are developed upon the surface; at the end of 

 forty-eight hours a collarette with irregularly festooned margins is devel- 

 oped around this central mass ; this is thinner and much more transparent 



