MEASUREMENT. xlv 



7. Millons test-liquid for proteine compounds. (See Millon's Test.) 



8. Ether or benzole dissolves fatty and resinous matters, &e. 



9. Chromo-sulphuric acid, or a mixture of solution of bichromate of potash and excess 

 of sulphuric acid, dissolves the intercellular substance of plants, thus isolating beautifully 

 the wood-cells &c, aud developes the starch-rings &c. 



10. Ammoniuret of copper, formed by digesting copper turnings in an open bottle with 

 solution of ammonia, rapidly dissolves cellulose. It must be used fresh. 



11. Dye-tests. — Carmine and ammonia, or the aniline-compounds, Judson's dyes, 

 magenta, picro-carmine, logwood, chloride of gold, picric acid, &c. are often used as such 

 (Staining). 



These are perhaps the most common reagents which the experimenter will be called 

 upon to use. A general plan for the qualitative analysis of substances must be obtained 

 from works upon chemical analysis. It may be remarked, however, that the qualitative 

 analysis of portions of a substance too minute to be more than barely discerned by the 

 naked eye, may be effected by the aid of the microscope. The use of the microscope in 

 strictly chemical investigations also, cannot be too highly recommended ; for it will 

 frequently throw great light upon the distinction of chemical precipitates of closely 

 approximative chemical properties. 



D. Measurement . 



A knowledge of the size of objects is of the utmost importance, and is frequently of 

 great assistance in the distinction of one object from another ; for many objects of totally 

 dissimilar nature present exactly or nearly the same appearances when examined with 

 differ ent powers. The dimensions should invariably be added to the description of micro- 

 scopic bodies ; and when figures are given, the number expressing the linear amplification 

 of the objects should be placed near them. 



Directions for determining the measurement of objects are given under the head 

 Measurement . It should always be expressed in fractions of an English inch. 



In conclusion, we must remark that the observations given in this Introduction are not 

 offered as by any means complete. However, we trust they will serve to show that there 

 are numerous means at command for determining the structure of objects, to indicate 

 the nature of these means, and that microscopic researches should be carried out upon 

 something like a definite plan. 



MICROSCOPIC ANALYSIS. 



The following list of miscellaneous matters, forming an analysis of the second part of 

 the Introduction, may serve to recall to the observer the most important points to be 

 looked for, and the means of discovering them. 



Microscopic Analysis. Form : — a, outline; b, rolling over; c, side view; d, endvieiv; 

 e, angles, goniometer. 



