34) Prof. Christison's Analysis of' the Hya-hya Tree. 



boiling potass undergoes no farther change than what occurs 

 in boiling water. Ammonia does not act on it. 



Muriatic acid has no effect on it. Strong nitric acid, either 

 cold, or aided by heat, has also hardly any effect ; it merely im- 

 parts a yellowish tint, and a slight increase in hardness, but 

 does not alter any other property. Strong sulphuric acid dis- 

 solves it readily, and acquires a dark brownish-black colour. 



The preceding experiments show that the concrete juice of 

 the Hya-hya tree consists of a small proportion of caoutchouc, 

 and a large proportion of a substance possessing in some re- 

 spects peculiar properties, which appear to place it intermediate 

 between caoutchouc and the resins, to the latter of which it 

 bears the greatest resemblance. It differs, however, from the 

 resins in being more easily fusible, in undergoing partial decom- 

 position at 212°, in being very sparingly soluble in hot alcohol 

 and caustic potass, and in resisting the action of strong nitric 

 acid. 



The information thus obtained from the chemical analysis of 

 the juice, will naturally raise considerable doubts with regard 

 to its possessing any nutritive quality. There is every reason 

 to believe that caoutchouc, wax, resin, oil, and other vegetable 

 principles, which resemble these in containing a large proportion 

 of carbon, and in being insoluble in water or acidulous fluids 

 aided by the action of heat, are very slightly nutritive, because 

 the stomach can digest but a small quantity of them, and that 

 only with great difficulty. The concrete juice of the Hya-hya 

 evidently belongs to this class of substances. It is soluble in 

 fewer menstrua than any of them, except caoutchouc ; and it 

 evidently contains a large proportion of ca.'-bon, as it burns with 

 a dense white flame and much smoke. There is great reason 

 to suspect, therefore, that it is not nutritive, and that, as an ar- 

 ticle of food, it can be useful only by rendering other aliments 

 agreeable. 



I need scarcely add, that the juice of the Hya-hya differs to-' 

 tally from that oZ the Palo df Vaca, the plant described by . 

 Humboldt as supplying the vegetable milk of the province of- 

 Caraccas, in South America *, as well as from the juice of (Tie 



• Ann. de Chim. et t\e Phvs. vii. 1827. 



