72 



STUDYING MOLDS, YEASTS, AND ACTINOMYCETES 



should be just hot enough to soften the cement so that it will adhere, 

 not enough to liquefy it so that it will run. One now has a culture 

 chamber arranged as shown in Fig. 29, with a space something less 

 than 1 mm. deep between the cover glass and the slide. A tube of 

 agar is melted, cooled, and inoculated with spores of the mold to be 

 studied. With a sterile capillary pipet some of the agar is transferred 



to the edge of the cover glass and allowed 

 to run under until part of the space has 

 been filled, as shown in the illustration. 

 If the shdes are prepared just before use, 

 they will have been sufficiently sterilized 

 by the heat used in their preparation. 

 They may then be incubated in a glass 

 staining jar containing moistened blot- 

 ting paper in the bottom. The lid of the 

 jar should be sealed with petroleum jelly or surgeon's plaster. After 

 growth has occurred, the arrangement of both the aerial and sub- 

 merged mycelium may be readily seen. Photomicrographs taken 

 from such slide cultures are shown in Figs. 30 and 46. Paraffin can 

 be used in the preparation and sealing of a culture cell of this type, 



Fig. 29. Method of grow- 

 ing molds between a slide 

 and cover slip. 



Fig. 30. Aspergillus sp., shoeing appearance of conidiophores as seen in a slide 

 culture of the type shown in Fig. 29. 



the sterile melted paraffin being handled in a sterile Pasteur pipet. 

 It is less permanent but more convenient. 



Microscopic Examination of Yeasts. The vegetative cells of yeasts 

 and the determination of their mode of reproduction (such as type 

 of budding and fission) are best determined in simple wet prepara- 

 tions made by mounting some of the growth from a young, actively 

 growing culture in a drop of water. Smears are not good because of 



