86 BACTERIA IN THE SPUTA 



nail, too much tartar is removed, which must be disintegrated 

 twice over ; first to select a particle, and then to thin and spread 

 it on the slide I have best succeeded with a bent needle, first 

 scaling lightly the labial surface of the tooth, and carrying the very 

 minute particle of the patina on to the slide (on which was placed 

 a drop of aniline water), and then scraping likewise the interstice 

 between the teeth, to place on the slide another similar particle. 

 In order not to spoil the fructifications, the scraping should be 

 made neatly from top to bottom. This manipulation should be 

 done in the morning, fasting, and cannot give good results in 

 those subjects who habitually clean their teeth with tooth-brush 

 and powders. 



Thus we get within the drop of aniline water two tiny islands 

 of Leptothrix, but they are yet too thick to be reduced to the thin- 

 ness required. We shall break them with the needles, so as to 

 carry on to the slide only a kind of whitish dust, which will occupy 

 a third of the area to be covered. Having done this, we shall add 

 with the rod another drop of aniline water, and soon after, with 

 a different rod, a drop of gentian violet solution. We shall speak 

 of the other colourings in Section 4, the treatment being nearly 

 the same. The preparation is kept for a little while under a glass, 

 and when it appears to the naked eye to be sufficiently coloured, it 

 is mounted without washing, which, in this case, would take away 

 all the fragments, the fructifications will be set free, and the bacilli 

 float about each tiny island. 



When we wish to examine together the saliva and the patina 

 dentaria, instead of placing a drop of aniline water previously on 

 the slide, we will put on it a drop of saliva in the manner we shall 

 indicate by-and-by ; the rest of the treatment is the same. How- 

 ever, the preparations without the saliva turn out clearer and 

 thinner ; whilst those mixed with it cannot become thin enough, 

 owing to the resistance presented by cumuli of large buccal epi- 

 thelia, which place themselves like supports between the slides ; 

 still worse when one of those cumuli happens to be on a bed of 

 Leptothrix. Naturally, in the preparations mixed with saliva, the 

 rich cumuli of Diplococci are more abundant, whilst they are 

 seldom found on those of the patina only. 



Lastly, the cover-glass is put on and gently pressed down with 



