104 BACTEBIOLOGY 



hyphee which rise free above the level of the gelatine are 

 put in motion by currents of air (such as lightly blowing 

 upon the plate culture), and when this occurs the shedding 

 of the spores can be readily observed. The earliest forma- 

 tion of spores occurs in the centre of the colonies, and is 

 indicated by a green coloration. 



Loffler's methyl blue stains the filaments of mycelium 

 and the hyphae, the spores on the other hand remaining 

 unstained. Moulds cannot easily be moistened with water, 

 as their surface has no affinity for it, owing to the presence 

 of a thin coating of fat ; hence the first proceeding is to 

 treat the unstained moulds with alcohol to which a little 

 ammonia has been added, after which they are examined in 

 glycerine and water or plain glycerine. For making per- 

 manent preparations, glycerine or glycerine jelly is suitable, 

 the cover-glass being cemented with asphalt lac dissolved 

 in turpentine over a water -bath. 



Hansen recommends the addition of 0-1 to 0-2 per cent, 

 of hydrochloric acid when growing moulds upon gelatine, in 

 order to keep away bacteria. 



Brown mould. — The fur formed by the hroivn mould de- 

 scribed by Hesse is brownish yellow, and is further distin- 

 guished from penicilium by its closely felted mycelium, the 

 hyphae being scanty, ramified, and segmented. Gelatine 

 is very rapidly liquefied, and in thrust-cultures becomes 

 softened with the mycelium of the fungus into a brown, 

 viscid, stringy mass. Growth takes place best at 15° to 20° C. 

 According to Trelease the mould is identical with an alga, 

 the Cladothrix dichotoma, very frequently found in water. 



Yeast. — This micro-organism consists of cells and 

 masses of cells of which the individual elements possess an 

 oval figure and multiply by gemmation. They have a 

 thin limiting membrane and a granular protoplasm con- 

 taining vacuoles (see fig. 6). They are obtained from the 



