78 POWDERED VEGETABLE DRUGS 



in the so-called arrow-root biscuit is 2.5 per cent. The micro-analyst's 

 estimates may range from a trace or small amount to 5 per cent. 

 When the quantities of admixtures are large, from 30 to 90 per cent., 

 the estimations may approximate within 10 or 15 per cent, of the 

 actual amount present. These estimates can no doubt be made 

 much more accurate by uniform methods of technique, aided by 

 certain mechanical devices. For example, in the examination of 

 vegetable powders, spices, meals, flours and similar substances, the 

 samples should be thoroughly mixed, and slide mounts should be of 

 standard and uniform thickness and the relative amounts of the 

 ingredients should be estimated by means of microscope slides having 

 uniform ruled squares of definite measuring value in microns. These 

 and other details in the methods should be more fully worked out. 



Several micro-analysts have declared themselves as opposed to 

 giving percentage estimates of the several ingredients of a compound. 

 However, not to give the approximate percentages will cause great 

 confusion and very materially lessen the value of the work done. For 

 example, to report a pancake flour as composed of ''buckwheat and 

 wheat flour, the former predominating," instead of "buckwheat 75 

 per cent, and wheat 25 per cent./' would certainly be unsatisfactory. 



Recently some dispute has arisen as to the relative value or im- 

 portance of the microscopical and chemical analysis of foods and drugs. 

 With certain substances the microscopical analysis is of first import- 

 ance, while with others the chemical analysis is of the greater value. 

 The following examples will serve to explain the relative value of 

 the chemical and microscopical analyses. Suppose the substance to 

 be examined is a baby food. The microscope may reveal approximate 

 percentages of oil globules, steam dextrinized wheat starch, unchanged 

 wheat and arrowroot starch, wheat tissue and milk sugar. The 

 chemical analysis will show a definite percentage of sugar, soluble 

 starch, insoluble starch, fat, vegetable fiber and ash. This is a good 

 example of a case where the two methods of analysis are of equal import- 

 ance; one without the other would be unsatisfactory, incomplete and 

 inconclusive. Again, the chemical assay may show that a sample of 

 powdered or crude belladonna leaf contains 0.35 per cent, of mydriatic 

 alkaloids, and yet the microscopical examinations may prove the 

 presence of from 20 to 30 per cent, of some foreign leaf. 



II. TISSUE TERMINOLOGY AND IDENTIFICATION OF TISSUES 



A uniform tissue terminology is essential to a comparison of results 

 in the critical examination of vegetable drugs and spices. That is 

 the names of tissues, tissue elements and of cell-contents, should be 



