190 THE MICROSCOPE. Dec. 



PRACTICAL SUGGESTIONS. 



By Iv. a. WILLSON, 



CLEVELVND, OUIO. 



Yeast Cells. — The examination of yeast affords a fine study- 

 in cell formation. 



For the purpose use a very small piece of compressed yeast, — 

 a piece no larger than half a join's head ; or scrape a very small 

 portion from a cake of yeast. Place the portion scraped off on 

 a plain glass slip, in a drop of water, cover and examine with a 

 quarter inch objective. Vvlien the cake of yeast is used the yeast 

 will be obscured by the large starch grains composing it. Re- 

 move most of the cells with the forceps before covering. 



The yeast plant is Saccharomyces cerevisisae. Notice the 

 mother cells and the daughter cells. These cells average .008 

 mm. or .0003 of an inch in diameter and reproduce the daugh- 

 ter cells by budding. ^ 



Another form is produced by division of the protoplasm with- 

 in the parent cell. By gently heating the slide after it is cov- 

 ered, the process of budding may be accelerated and beautifully 

 displayed upon the slide. 



It may be better seen by keeping the covered slide in a warm 

 moist chamber for some hours. The daughter cells may be de- 

 veloped by growing yeast upon fresh cut slices of potato kohl- 

 rabi, carrot or upon small slabs of plaster of Paris. The pre- 

 parations must be kept moist by covering with a bell jar and 

 may be seen in a week or ten days from the beginning of the 

 experiment. 



Pus Cells. — It is interesting to examine pus by covering and 

 examining with a quarter inch objective ; then remove the slide, 

 lift the cover and pla-ie a drop of acetic acid upon the specimen, 

 and examine. Upon the second examination each cell will ex- 

 hibit from one to four nuclei. 



Carbolic Acid for Mounting. — This is a valuable medium 

 for mounting. Ordinary alcohol used in mounting insects 

 makes them stiff and hard; but carbolic acid penetrates the 

 specimen and readily mixes with other fluids used in mounting, 

 such as water, glycerine and Canada balsam. 



