CELL-CONTENTS A'ND FORMS OF CELLS. 173 



din, a glucoside, are not only products of constructive metabolism, 

 Hbut are entirely reassimilated. 



SUBLIMABLE PRINCIPLES. Quite a number of plant principles 

 are capable of being sublimed. Not only is this true when they are 

 in the pure state, but also when they are associated with other 

 compounds in the plant cell. This fact is of very great interest in 

 the examination of commercial articles and also in the study of 

 the localization and distribution of plant constituents. The method 

 of procedure is very simple, and a small quantity of material 

 only is necessary, usually from 0.020 to 0.050 Gm. being required. 

 In the study of leaves a fragment about 10 square millimeters is 

 sufficient. The material is dried, either cut up or more or less 

 comminuted and placed in a small watch crystal, the latter being 

 covered either with a slide or another watch crystal for the deposi- 

 tion of the sublimate. The watch crystal containing the material 

 is carefully heated either on a sand bath or on a bath containing 

 sulphuric acid (Figs. 101 to 104). 



Rosenthaler (Ber. d. d. pharm. Ges., 1911, p. 338) has sug- 

 gested in the examination of powdered drugs a specially con- 

 structed apparatus. A small quantity of the powder is intro- 

 duced by means of a long funnel into a suitable tube, so that nene 

 of it comes into contact with the side walls. The powder should be 

 covered with a layer of asbestos to prevent any of it being carried 

 up mechanically. The tube is closed with a rubber stopper having 

 two holes, one of which carries a doubly bent tube leading to a 

 small vessel acting as a receiver, the other carrying a tube con- 

 nected with an air-pump. The air is exhausted and the tube con- 

 taining the drug is heated in a bath of sulphuric acid or paraffin. 

 A sublimate will form in the upper part of the tube containing 

 the material, and distillation products will pass into the tube 

 acting as a receiver and can be tested with various' solvents and 

 reagents. Plants containing thein, vanillin, and coumarin may be 

 examined by direct sublimation in a watch crystal. Substances 

 which yield tarry distillate, as cinchona, hydrastis, piper, etc., 

 probably are better examined using the apparatus described by 

 Rosenthaler. 



Tunmann (Ber. d. d. pharm, Ges., 1911, p. 312) examined a 

 number of plants of the Ericaceae and found, by the microsublima- 



