502 



POWDERED DRUGS 



The action of any of the clearing agents mentioned above may be 

 hastened or increased by the application of heat. By holding a mounted 

 specimen over the flame of an alcohol lamp or a Bunsen burner it can be 

 heated without injury, even to boiling, if proper care be exercised. 



For more detailed directions for the use of reagents see Chapter II, 

 on Reagents and Processes, where a complete list of them is discussed 

 and explicit directions given for their use. This list of reagents is arranged 

 alphabetically and is in convenient form for handy reference. 



tm. 





PIG. 275. Powdered Rhamnus Frangula Bark. (X 210.) col. Collenchyma of the cortex. 

 cr. Prismatic and rosette crystals, fl. Bast fibers with pitted walls. /, /', Bast in longitudinal and 

 transverse section. PC, p'c'. Cortical parenchyma, in longitudinal and transverse section, ph. 

 Phelloderm. rm, r'm'. Medullary ray in tangential and radial section, it's', Cork in tangential 

 and transverse section, tc, Rows of crystal cells. (From Greenish and Collin.) 



Measurements. The fragments of powders should be carefully meas- 

 ured, and the measurements used for comparison wherever it is possible 

 to do so. Measurements should be made with an eye-piece micrometer. 

 In preparing specimens for measurement the greatest care should be ex- 

 ercised in the use of reagents so that objects may not be swollen abnor- 

 mally or distorted before measurements are made. 



On the following pages are given a few examples to show the diagnostic 

 characteristics of some powders which frequently, either by mistake or 

 intentionally, are substituted one for the other. 



