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Leptothrix. 



Varieties of Leptothrix are common in the mouth and 

 slime of the teeth. L. buccalis is a term perhaps compris- 

 ing several species, some of which may cause dental 

 caries. The threads have been thought to penetrate 

 the tissue of the teeth, after the enamel has been acted 

 upon by the acids generated by bacteria, including the 

 fermentation of the food. 



L. innominata (Miller), commonly found in the deposit 

 on teeth, does not give the blue granulose reaction when 

 treated with dilute sulphuric acid and iodine. This 

 distinguishes the organism from L. buccalis maxima which 

 gives the blue granulose reaction. 



It is an open question whether all the Leptothrices 

 in the mouth are not either bits of the same or stages in 

 the life of the same. 



Leptothrix epidermidis. A non-pathogenic sporulating 

 organism found in variolous crusts and on the skin 

 between the toes. 



Cladothrix Dichotoma. 



This organism, which is common in natural waters, 

 consists of long motionless filaments, sometimes a milli- 

 metre in length, which may possess pseudo-branches. 

 The sheaths of the filaments are often coloured yellow, 

 red, olive-green, or brown by oxide of iron. The 

 C. diclwtoma withdraws iron from water, and thus fixes 

 it, often causing obstructions in iron pipes. On gelatin 

 plates it forms small yellowish dots surrounded by a 

 brown halo, and a depression due to the slow liquefaction 

 of the gelatin. On agar it grows at 35 C. as a thick 

 shining expansion, which adheres so closely to the medium 

 that it is impossible to remove it without carrying away 

 some of the agar. The growth has a tendency to form 

 concentric rings, and sometimes becomes covered with a 

 greyish efflorescence, which is dry and very brittle. The 

 agar becomes brown in colour. All the cultures have a 

 very strong mouldy smell. 



Beggiatoa. 



Beggiatoa arej found in both fresh and salt water; 

 in sulphur springs and brewery effluents they are 



