BACTERIA OF THE MOUTH. 339 



special conditions, as yet not at all understood, for their 

 existence, and although one or other of them may be found 

 in enormous numbers in one case, and may be comparatively 

 few in another, there is usually some explanation to be 

 offered for such preponderance. 



(1) The Leptothrix innominata (Miller) is found, usually, on the soft 

 white material that is deposited on teeth, it may probably be out a generic 

 term for more than one form, as the constituent elements of which it is said 

 to be made up vary very much both in length and in thickness ; they are 

 usually .5 to .8/* thick, and though there may be shorter cells or rods, 

 the organisms usually consist of tortuous non-motile threads. These rods 

 and threads as a rule contain no spores. 



(2) The second form, Bacillus buccalis maxtmus, occurs as isolated 

 bacilli or threads, generally arranged in bundles, which may interweave 

 with one another. These bundles are sometimes of very considerable 

 length, but each thread is divided into short rods, from I to i.2/i broad, 

 and from 2 to io/i long. This bacillus is, as a rule, not found within the 

 dentine tubules. In addition to this bacillary form there is a leptothrix 

 form, in which the filaments are considerably longer, but otherwise the 

 organism is much like that already described, although it is scarcely to be 

 looked upon as related to the leptothrix innominata. 



(3) The next organism is one called by Miller the lodococcus vaginatus, 

 which is found especially in mouths that are not properly cleansed ; it appears 

 to be made up of cocci arranged as diplococci or tetrads, which are usually 

 arranged and held together in a kind of sheath, though now and again a 

 single coccus or diplococcus may be seen, around which no sheath can be 

 demonstrated. When this organism is stained with iodine a marked 

 reaction is obtained, the sheath being stained yellow, whilst the cocci are 

 stained dark blue. 



One of the most interesting forms met with in the mouth is : (4) the Spiril- 

 lum sputigenum (Miller), which always occurs in certain numbers, but is found 

 in especially large quantities in those cases in which the presence of tartar has 

 set up slight inflammation of the gums around the teeth ; it usually occurs 

 in the eedematous gum just at its junction with the teeth. This organism 

 has more than usual interest from the fact that it was for long supposed, by 

 Lewis and Klein, to be identical with the cholera bacillus. Morpho- 

 logically it certainly resembles this latter organism in many respects. The 

 simplest form is that of a small curved bacillus ; sometimes two or three 

 of these may be joined together to form an S-shaped organism, whilst in 

 other cases it may be found as long spiral threads. This organism, as we 

 have said, is almost invariably met with in the mouth, but it is curious 

 that it is very seldom found between the teeth, or in carious cavities ; it 

 thrives apparently upon the exudation from the slightly inflamed gums, and 

 so necessary is this food for its existence that it has never yet, so far as is 

 known, been cultivated in any of the artificial nutrient media outside the 

 body, although (5) a somewhat thicker, curved, comma-shaped bacillus, 

 identical in almost every respect (except as regards size), can be cultivated 

 in gelatine quite readily at the ordinary temperature of the room. This 

 differs from the first-mentioned in that it has the true comma-shape, tapering 

 towards one end. 



