PREPARATION OF BREAD-FLASKS. 395 



The sterile bread-flasks are inoculated with the follow- 

 ing' moulds: 



Penicillium glaucum. Aspergillus niger. 



Mucor corymbifer. Asperglllus flavescens. 



Mucor rhizopodiformis. Aspergillus fumigatus. 



All these flasks, except the first, should be placed in 

 the incubator at about 37, for 24 to 36 hours. They should 

 then be examined for the characteristic fruit-organs and 

 for spores. A portion of the growth for this purpose is 

 transferred to a watch-glass containing some 50 per cent, 

 alcohol, to which a drop or two of ammonium hydrate has 

 been added. When the growth becomes moist, it should be 

 transferred to a drop of glycerin on a slide. The specimen 

 is thoroughly and carefully teased with needles or pins. It 

 is finally covered with a glass-slip and examined with the 

 No. 7 objective. 



If the specimen is satisfactory it may be made perma- 

 nent by placing a ring of asphalt, with the aid of a turn- 

 table, around the edge of the cover-glass. Although the 

 moulds stain readily by the simple and by Gram's method, 

 it is not advisable to prepare dried specimens owing to the 

 alteration which results during desiccation. 



In this laboratory it is customary to study the yeasts 

 and moulds at the close of the work on non-pathogenic 

 bacteria. The parasitic skin moulds and the streptothrix 

 forms are studied in connection with the pathogenic 

 bacteria (see p. 316). 



