80 BACTERIA IN THE SPUTA 



on the tongue or teeth. But, owing to the continual friction on 

 the tongue and teeth, the growth cannot reach the fourth period, 

 or that of fructification. Then we have bare growths apparently 

 sterile, as represented above. The same happens with the tufts of 

 Leptothrix, often found on the epitheUum scales, on the residue of 

 undigested food, or other corpuscles in urine, sputa, etc., forms 

 which may be called " aerial," although incomplete, " vegetation." 



But in many parts of the dental surface, where there is less 

 friction, as between tooth and tooth and near the gums, the fourth 

 phase or fructification takes place. This fact has not been ob- 

 served, and is not even suspected, as we gather from the most 

 recent work of Miller. "^'^ 



I call it aerial vegetation, because the stems of the microphite 

 have a tendency to rise in the air, although immersed like 

 the algae. In our case the surrounding liquid is the saliva. This 

 fructification by spores, first noticed and investigated by me, con- 

 sists of comparatively long ears (Figs. lo, ii, 12, 13, 16), 

 formed by the exudation of a viscous substance, faintly coloured, 

 round the ends of fertile filaments. In this substance are entan- 

 gled small round spores, often brightly coloured, placed in six 

 longitudinal lines, as we shall see later. In the strongest speci- 

 mens (Fig. 16,/, g) as many as 720 spores can be counted in an 

 ear. All the cocci and minute bacteria are probably dissemina- 

 tions from these spores. 



There is another form of special production, or pseudo-inflo- 

 rescence, which is drawn in Fig. 14, ^, ^, <:, resembling points^ 

 round a filament or group of fertile filaments. These points 

 having fallen off form the nail-like, snake-like, or comma bacilli. 

 If we admit the analogy of these bacilli with the reproductive 

 filaments of other cryptogams, Leptothrix may be compared to 

 a fungus, or dioecious alga, with two sexes upon different fila- 

 ments ; and such pointed productions would exhibit the male 

 organs, the elements of which, spread about the surrounding 

 medium, would, with their great mobility, act as antherozoids in a 

 manner not yet known to us. In such an hypothesis, the 

 scanty number of such inflorescences, with regard to fructifica- 

 tion or female organs, would be fully explained. Therefore, 



*W. D. Miller, Die Mikro-Organisnien der Mundhohle, etc., 1889. 



