78 



PREPARATION OF BREAD FLASKS. 



Moist bread, like potatoes, owing to its slightly acid 

 acid reaction, is an excellent medium for the growth of 

 some organisms, especially moulds. 



Prepare some dry powdered bread, which can be read- 

 ily done by over-toasting it in the dry-heat oven, and then 

 crushing or pulverizing the dry mass. Keep in a stoppered 

 bottle. 



Clean, plug, and sterilize in the dry-heat oven six 

 small Erlenmeyer flasks. When cool cover the bottom of 

 the flasks to a depth of about ^ inch with the dry powdered 

 bread, then add water till the mass becomes thoroughly 

 moist and soft. Sterilize in steam sterilizer for three con- 

 secutive days, \ hour each day. 



Inoculate the bread flasks with the following moulds : 

 Penicillium glaucum. 

 .Mucor corymbifer. 



" rhizopodiformis. 

 Aspergillus niger. 



" flavescens. 



" fumigatus. 



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

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

 should then be examined for the characteristic fruit organs 

 and spores. Transfer a portion of the growth to a watch- 

 glass containing about 50 per cent, alcohol, to which a 

 drop or two of ammonium hydrate has been added. When 

 the growth becomes moist, transfer a portion to a drop of 

 glycerine on a slide. Tease out the specimen thoroughly 

 and carefully with needles or pins. Cover with a cover- 

 glass and examine with No. 7 objective the fruit organs 

 and the structure. If the specimen is satisfactory it may 



