1 20 Lectures on Bacteria. [^ xi. 



are over i /* in the transverse diameter, others only half that 

 thickness. The length also of the members (cells) is unequal, 

 in some cases not exceeding the transverse diameter, in others 

 several times greater. The filaments, especially those with 

 short and thick cells, often show the reaction of granulose 

 (page 5), but different portions of the same filament may assume 

 alternately a blue and yellow colour with iodine. Rasmussen 

 (54) claims to have distinguished three separate forms of Lep- 

 tothrix buccalis by aid of cultivation. I cannot say whether 

 this is rightly done or not, for Rasmussen's work is only known 

 to me at second hand. 



Secondly, the masses of Leptothrix often contain round Cocci, 

 which are sometimes irregularly rolled up into dense gelatinous 

 heaps, and like the Leptothrix-forms are without the power of 

 motion (Fig. 16, m). 



Thirdly, a Spirillum-form is commonly found with the others, 

 showing itself rather in single specimens and in the fluid sur- 

 rounding the Leptothrix-masses after addition of water ; this is 

 Spirochaete Cohnii, Winter (S. buccalis or S. dentium), and 

 consists of filaments of extreme tenuity without evident trans- 

 verse divisions, spirally twisted into 3-6 or more steep 

 and often irregular coils, flexible and either exhibiting a slow 

 twisting movement or else without motion (Fig. 16, e). 



Lastly, one more form is often though not always observed 

 with the others, a thin short rod-shaped Bacterium, bent like 

 a bow, and described first by Miller and then by Lewis (55) 

 as the comma-bacillus of the mucus of the mouth (Fig. 16, d); 

 in a fluid it usually exhibits an active hopping movement. 



It may be assumed beforehand as certain, that besides these 

 forms other saprophytic Bacteria must also occur in the mucus 

 of the mouth. Miller, according to recent communications, has 

 found twenty-five such organisms. Hueppe speaks of two 

 Micrococci which produce lactic acid as coming from the human 

 mouth (see page 94). But other forms do not appear to be 

 developed in any abundance in healthy individuals. It may be 



