242 BACTERIOLOGY 



biologically resemble those of diphtheria, but are devoid of 

 virulence, and these are consequently described as pseiido- 

 diphtheritic bacilli. Eoux and Yersin, however, believe 

 them to be genuine diphtheria bacilli the virulence of which 

 has become very much attenuated. 



Spirillum Milleri. — Miller isolated from a carious tooth a 

 variety of bacterium which appears to be identical with the 

 vibrio described by Finkler and Prior. It consists of jointed 

 rods, sometimes more and sometimes less curved, the figure 

 of which resembles S or O. The spirilla are destitute of 

 motility. Upon the gelatine plate there appear scattered 

 colonies, which speedily liquefy. Thrust-cultures show no 

 air-bubble at the surface, owing to the rapidity with which 

 liquefaction progresses, but there soon forms a tolerably ex- 

 tensive funnel-shaped fluid area, on the bottom of which the 

 masses of bacilli lie (compare fig. 52). A superficial layer 

 forms upon agar. The micro-organism seems to take a 

 prominent part in the softening and liquefaction of the 

 enamel organ which occurs in caries. 



Spiroclisete dentium (Denticola). — There is found in the 

 cavity of every mouth, according to Miller, and particularly 

 below the edge of the gum, a variety of spirillum which is 

 also met with in the secretion of the nose, and is remark- 

 able for the fact of having pointed ends. This peculiarity 

 is only seen in two of the forms of spirilla discovered up to 

 the present, viz. the SjnroclKste dentium and the spirillum 

 of recurrent fever. Artificial cultivation has not yet been 

 successful. 



Vibrio rugula. — Vignal found also an anaerobic micro- 

 organism in the mouth, which, however, can only be pre- 

 served in an indifferent gas, such as hydrogen. Yellowish- 

 white globular colonies develop on the gelatine plate, and 

 liquefy outwards from the periphery. In thrust-cultures 

 little white nodules form on the surface as early as the first 



