On the Elaflic Gum-Fine, and the Ujes of its Milk. 535 



In my numerous attempts to trace this vine to its top, I never fucceeded ; for, after 

 following it in its different windings, fometimcs to a diftance of two hundred paces, I loft 

 it, from its afcending among the branches of trees that were inacceflible either from their 

 fize or height. On the weft coaft of Sumatra I imderftand they have been more fuccefsfulj 

 Dr. Roxburgh having procured from thence a fpecimen of the vine in flowers, from which 

 he has claffed it ; but whofe defcription I have not yet feen. 



With us the Malays have found tafting of the milk the beft mode of dlfcriminating be- 

 tween the elaftic gum vine, and thofe which refemblc it in giving out a milky juice, of 

 which we have a great variety ; the liquid from the former being much lefs pungent or 

 corrofive than that obtained from the latter. 



The ufual method of drawing off the milk is by wounding the bark deeply in different 

 places, from which it runs but flowly, it being full employment for one perfon to colledl a 

 quart in the courfe of two days. A much more expeditious mode, but ruinous to the 

 vine, is cutting it in lengths of two feet, and placing under both ends veffels to receive 

 the milk. The beft is always procured from the oldeft vines. From them it is often 

 obtained in a confiftence equal to thick cream, and which will yield two thirds of its 

 own weight in gum. 



The chemical properties of this vegetable milk, fo far as I have had an opportunity of 

 examining, furprifingly referable thofe of animal milk. From its decompofition in con- 

 fequence of fpontaneous fermentation, or by the addition of acids, a feparation takes place 

 between its cafeous and ferous parts, both of which are very fimilar to thofe produced by 

 the fame proceffes from animal milk. An oily or butyrous matter is alfo one of its com- 

 ponent parts, which appears upon the furface of the gum fo foon as the latter has attained 

 its folid form. The prefence of this conliderably impeded the progrefs of my experiments, 

 as will be feen hereafter. 



I was at fome trouble in endeavouring to form an extraft of this milk fo as to approach 

 to the confiftence of new butter, by which I hoped to retard its fermentative ftage, with- 

 out depriving it of its ufeful qualities j but as I had no apparatus for diftilling, the furface 

 of the milk, that was expofed to the air, inftantly formed into a folid coat, by which the 

 evaporation was in a great degree prevented. I, however, learned, by colledling the 

 thickened milk from the infide of the coats, and depofiting it in a jelly pot, that, if ex- 

 cluded from the air, it might be preferved in this ftate for a confiderable length of time. 



I have kept it in bottles, without any preparation, tolerably good, upwards of one year; 

 for, notwithftanding the fermentation foon takes place, the decompofition in confequence 

 is only partial, and what remains fluid, ftill retains its originJil properties, although con- 

 fiderably diminiftied. 



Not having feen A^. Fourcrofs memoir on Caout-chotic, I could not make trials of the 

 methods propofed by him for preferving the milk unaltered. 



In making boots, gloves, and bottles, of the elaftic gum, I found the following method 

 the beft: I fir ft made moulds cf wax, as nearly of the fize and fliape of what they repre- 



c> Z 2 fented 



