CULTIVATION OF MOULDS. 155 



water for five minutes, and then placed in a 5 per cent, acetic 

 acid solution for a few minutes. They are 'stained with a 

 strong anilin gentian-violet stain. The staining is greatly 

 facilitated if the stain or the preparation covered with stain 

 is heated gently. 



Moulds are cultivated just like the bacteria, except that the 

 medium must have an acid reaction. Bread-pap is a most 

 useful culture-medium, and is used very widely for this pur- 

 pose. The aspergillus will outgrow any of the other moulds, 

 and in order to get a pure culture of any one mould it will 

 be necessary to inoculate an animal by injecting the mould 

 in water into the abdominal cavity. The different varieties 

 will separate and form colonies as the bacteria do on a plate 

 or Petri dish culture. There is no necessity, however, for 

 making pure cultures of the filamentous fungi, as they can 

 be studied in a mixed culture just as well. 



