144 POWDERED VEGETABLE DRUGS 



it is about to be used. After the substance has been drawn up into 

 the pipette, and before delivery upon the slide, touch the delivery end 

 of the pipette upon a clean glass surface, and similarly touch the pipette 

 upon the slide after the desired amount (^o cc -) shall have been de- 

 livered. Spreading must be done carefully. If too much heat is 

 used in drying the material is apt to peel off; especially is this likely 

 to occur if oil or fat is present, as in milk. Excess of fat and oil may 

 be removed from the slide mount after drying and dehydrating with 

 alcohol, by dipping a few times into xylol or benzol, or ether. 



In a general way, the Loeffler stain will be found most useful for 

 purposes of differentiating between bacteria and non-bacterial particles. 

 Ziehl's stain will be found especially useful if it is suspected that the 

 substance under examination contains acid fast bacteria. It is a 

 diffuse stain and demands the careful use of the decolorizing agent 

 (acidulated alcohol). The Broca stain is especially recommended in 

 cases where it is desirable to differentiate between dead and living 

 bacteria (that is dead, or living at the time that the stain was applied). 

 In brief, the Loeffler stain will be employed for routine purposes, and 

 the others for occasional special purposes. 



For making the yeast and spore counts, use the ^50 cmm. areas 

 of the hemacytometer, sampling, mixing and diluting as for the bac- 

 terial count. The staining method is rarely if ever required for making 

 spore or yeast counts, as these structures are not likely to be confused 

 with anything else. The spore count is not a reliable indicator of the 

 amount of mold decomposition. It simply indicates that the mold 

 present had proceeded to the spore forming stage. A vegetable prod- 

 uct (as catsup, jam, jelly, preserve, etc.,) may be completely de- 

 composed by mold and yet the spores may not be abundant. On the 

 other hand, abundant spores does indicate a high degree of mold 

 contamination. 



If it is desired to determine the relative or comparative degree of 

 bacterial, yeast or mold decomposition, the following procedure is to 

 be followed. After having made the counts as above indicated, place 

 a small amount (5 cc. or 5 grams) of the substance under examination 

 in a clean beaker, and set aside in an incubator at a temperature of 

 37C. for a period of five days, by which time complete decomposition 

 (bacterial as well as mold, and perhaps also yeast) will have taken 

 place. Again make the desirable counts and compare the two findings, 

 and from such comparison deduce the percentage of decomposition 

 in the substance at the time the original examination was made. We 

 will suppose that the original examination of a fruit product gave the 

 following results : 



