248 APPLIED BACTERIOLOGY 



frequently found in sour milk and butter. The fibres of 

 the mycelium grow upwards, become segmented, and 

 support cylindrical conidia. The fungus grows on gelatine 

 without liquefying it, diffusing at the same time an odour 

 of sour milk. On agar it grows in the form of little stars, 

 which then overgrow the medium. In a thrust culture the 

 fibres of the mycelia are seen to permeate the medium. 

 Oidmm lactis grows very readily in milk, which it does not 

 change in any special way. It is not pathogenic in man or 

 animals. 



Oidium Albicans. — The fungus causing the white patches 

 occurring on the mucous membrane of the mouths of infants, 

 known as ' thrush,' was formerly assigned to the group 

 oidium, and described as Oidium 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 Schbnleinii) and 

 pityriasis versicolor (Microsporon fim-fur) 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 Lbffler's methylene blue, 

 which stains the filaments of the mycelium and hyphse, the 



