210 BACTERIA 



under the microscope. If treated with a solution of ferro cyanide 

 of potash and acetic acid, these stained parts turn a dark brown, 

 showing that there is an actual absorption or perhaps chemical 

 union of the protoplasm of the mould with the copper. Some 

 moulds are stained a deep blue, and are visible to the naked eye in 

 test-tubes, after treatment with the boiling alkaline copper others 

 are colored a bright yellow. Some moulds and bacteria have the 

 power of reducing copper in Fehling's solution. 



Diseases due to these forms are practically confined to the skin 

 although extremely rare cases of dissemination are on record. 



Ringworm of all kinds is due to the mould Trichophyton either of 

 the species megalosporon or microsporon. The spores of the 

 former are 7-8^, of the latter 2-3^. They grow readily as dis- 

 crete mammillated fluffy colonies. They consist under the micro- 

 scope of slender septate hyphae. 



Favus is due to the mould Achorion Schoenleinii. This fungus 

 gives off hyphae with knob-like reproductive organs. Spores are 

 oval 3-8/1X3-4^- This fungus grows as a "scutulum" on the 

 skin eruption. It can be cultivated on sugar agar, as a waxy, or 

 downy yellow or white round plate with a central mammillation. 



Pityriasis versicolor is due to the mould Microsporon furfur. 

 It is similar to the Trichophyta, but only invades the supeificial 

 layers of the skin. 



