1 88 BACTERIOLOGY. 



trate the tissue of the teeth, after the enamel has 

 been acted upon by acids generated by the fer- 

 mentation of food. The short reds, long rods, 

 cocci, leptothrix-forms, and screw-forms are found 

 in the dental canals. 



METHODS OF STAINING THE LEPTOTHRIX BUCCALIS. 



The threads of leptothrix buccalis have a special staining 

 reaction (Leber). They become coloured if in an acid 

 medium with iodine ; if the medium is alkaline, it must be 

 acidified with very dilute hydrochloric acid or acetic acid, 

 and the filaments then stained with iodine. The contents 

 are stained violet, and contrast with the sheath and septa, 

 which remain uncoloured. 



Leptothrix gigantea, Miller. Long rods, 

 short rods, and cocci, can be observed in the same 

 thread. There are also screw-threads, which may 

 take the form of spirals, vibrios, or spirochsete. 

 The threads increase in diameter from base to 

 apex, and corresponding with the thickness of the 

 threads, the rods and cocci show different dimen- 

 sions. They have been observed in the diseased 

 teeth of dogs, sheep, cats, and other animals. 



GROUP IV. CLADOTRICHE^E. 

 Genus L Cladothrix. 



Cladothrix dichotoma, Cohn. Threads re- 

 sembling those of leptothrix ; slender, colourless, 

 not articulated, straight or slightly undulated, and 



