46-i COMPOUND PRODUCTS. CHAP. I. 



addition of water again precipitated. They had all 

 the properties of resin. The remaining third part 

 possessed the properties of woody fibre. The same 

 experiment was tried on the juice of a variety of 

 other plants, and the result uniformly was that oxy- 

 muriatic acid precipitated from them woody fibre.* 



The virtues of plants have generally been thought 

 to reside in their proper juices, and the opinion 

 seems indeed to be well founded. It is at least 

 proved by experiment in the Poppy, Spurge, and 

 Fig. The juice of the first is narcotic, of the two 

 last corrosive. The diuretic and balsamic virtues of 

 the Fir reside in its turpentine, and the purgative 

 property of Jalap in its resin. If sugar is obtained 

 from the sap of the Sugar-cane and Maple, it is 

 only because it has been mixed with a quantity of 

 proper juice. The bark certainly contains it in 

 greatest abundance, as may be exemplified in 

 Cinnamon and Quinquina. But the Peach-tree fur- 

 nishes an exception to this rule : its flowers are 

 purgative, and the whole plant aromatic ; but its 

 gum is without any distinguished virtues. 



Malpighi regarded the proper juice as the prin- 

 ciple of nourishment, and compared it to the blood 

 of animals ; but this analogy does not hold very 

 closely. The sap is perhaps more analogous to the 

 blood, from which the proper juice is rather a 

 secretion. In one respect, however, the analogy 

 holds good, that is, with regard to extravasated 

 * Ann. dc China, vol. xxi. p. 285. 





