AND CONTENTS OF THE MOUTH. 75 



Another analogical proof we have in b^ where a bacillus, opaque 

 for five-sixths of its length, exhibits the other one-sixth clear and 

 slightly coloured. This specimen was taken from the saliva. 



In c we find four types — viz. : a short, clear segment above, 

 and on the top of it a bacterium of elliptical form ; in the middle, 

 a long, opaque segment ; and in the lower part a pale, granular 

 segment like the middle feature of type n' (Fig. 2) and types e and 

 / (Fig. 5). This specimen was also taken from the saliva. 



d. — This short but large bacillus, taken from the patina den- 

 taria (magnified to 2,500 diameters), exhibits the upper part 

 opaque and deeply coloured ; the other part is divided into two 

 segments. The middle segment is very short, clear, and contains 

 a dumb-bell bacterium placed across ; the lower one is opaque, 

 but not entirely, as there is on the right a clear space between the 

 opaque part and the outline, and presents a kind of indentation. 

 Other bacilli have the same features towards the edges, or near the 

 junctions of their segments. 



As regards the enclosed bacterium, there is no doubt about its 

 position in the envelope of the bacillus, from the look of the spe- 

 cimen as well as from the oscillation of the preparation, in which 

 the bacterium was seen to be always inside. In the preceding 

 specimens we have also abundant proof of this fact. 



Now in the first place, it shows that not only elliptical, very 

 minute, and linear bacteria, but also dicmb-bell bacteria, may be 

 found in the envelope of the bacilli ; from which we conclude 

 there is no difference between the dumb-bell bacteria and the 

 bacilli. And since the small chains, and the bundles especially, 

 adhering to the tongue, are mostly formed of dumb-bell bacteria, 

 we must infer the analogy of those forms with the baciUi, and 

 consequently of both to the Leptothrix. 



In the second place, comparing the various specimens of bacilli 

 (as a and d), containing bacteria with the fertile filaments of Lep- 

 tothrix, we find in the latter a variable disposition of internal 

 granules, or buds, adhesive to the envelope. Some are alternate ; 

 others on the same level at both sides. If we imagine that in 

 those filaments the buds grow up towards the middle line of the 

 stem, It will result that, when the left bud is placed higher than 

 that on the right, the bacteria resulting from their increase will 



