SYSTEMATIC AND DESCRI 



in the absence of sulphur, and from Crenothrix by 

 its wanting a sheath. They occur attached to crabs 

 (Gammarus locus fa) in sea water. 



Genus IV. Leptothrix. 

 SPECIES. 



ASSOCIATED WITH DISEASE : 



Leptothrix buccalis . . Saprophytic. 



Leptothrix gigantea ... ,, 



Leptothrix buccalis, Robin. Long, thin 

 threads, *7 i p, broad, colourless, often united in 

 thick bundles or felted together. Masses of cocci 

 occur with the threads, and the threads themselves 

 are composed of long rods, short rods, and cocci. 

 The threads may break up into spiral-, vibrio-, and 

 spirochseta-forms. The last-named occur in large 

 numbers in the mouth, and have been named Spiro- 

 chccte buccalis. The Leptothrix buccalis is found 

 in teeth slime, and is believed to be intimately 

 connected with dental caries. The threads pene- 

 trate the tissue of the teeth, after the enamel has 

 been acted upon by acids generated by the fer- 

 mentation of food. The short rods, 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 



