324 APPLIED BACTERIOLOGY 



oidium, and described as Oidiuvi albicans, but according to 

 Eees and Kehrer it belongs to the yeast fungi, and must be 

 spoken of as Mycoderma albicans (see p. 230). 



Trichophyton tonsurans, the fungus occurring in herpes 

 tonsurans, which is also stated to be the exciting cause of 

 impetigo contagiosa (an exanthem characterized by the 

 formation of pustules), eczema marginatum, tinea carcinata 

 (common ringworm), and onychomycosis (an affection of 

 the nails) ; the^fungus of favus (Achorion Schonleinii) and 

 pityriasis versicolor (Microsporon furfur) are morpho- 

 logically identical, as far as is at present known, with the 

 Oidium lactis. For further description of these see p. 230 

 et seq. 



Microscopical Examination of Moulds. — Moulds cannot be 

 easily moistened with water, owing to the presence on their 

 surface of a very thin layer of fat ; hence a portion of the 

 mould is treated with alcohol to which a little ammonia 

 has been added ; this removes the fat, after which they can 

 be mounted in glycerine or glycerine and water. If pre- 

 ferred, they can be stained with Loffler's methylene blue, 

 which stains the filaments of the mycelium and hyphie, the 

 spores remaining unstained. For permanent preparations 

 the moulds are best mounted in glycerine jelly, the cover- 

 glass being ringed with varnish to preserve the specimen. 



Culture of Moulds. — Hansen recommends the addition of 

 0*1 to 0*2 per cent, of hydrochloric acid to the culture 

 medium, in order to restrain the growth of bacteria. 



ALG.ffi. 



A number of the minute water-plants known as the algse 

 are included with the micro-organisms. They are classed 

 in two main divisions, Leptotrichece and Cladotrichem. 



The Leptotrichece are divided into three genera, viz., 



