42 Gum. [Book VIII. 



flight tinge of colour, generally yellow ; eafily foluble 

 in water into a vifcid liquor, called mucilage, in which 

 ilate it originally exifted in the vegetable j not acted 

 on by fpirit of wine or oils j not volatile in the heat 

 of boiling water, nor fufible in any heat, but fubject to 

 the fame changes as other vegetable matter. 



Gum, in its dry and folid ftate, is not in the leaft acted 

 on by oils, but mucilage manifefts a confiderable dif- 

 pofition to unite with them. Gum is not a folvent of 

 refmous or balfamic matter ; this matter will, how- 

 ever, be difTolved in water, in confequence of being 

 added to gum, efpecially by the afiiftance of agitation. 

 Thus oils and balfams may in many cafes be combined 

 with water, and remain combined with it, forming a 

 milky folution, particularly if the quantity of gum is 

 confiderable. This kind of combination is very fre- 1 

 quent in plants. There are many in which oil and gum, 

 are naturally united. The ufeful juice of the poppy 

 is of this kind, and from fuch compounds gum-refins 

 are obtained, by the evaporation of their watry parts. 

 Thefe compounds have full fallibility in water, though 

 the gum is the part chiefly difiblved; the refmous part is 

 either left in its concrete ftate^' or being merely fuf- 

 pended, and not difiblved, its particles are interpofed 

 between thofe of the gum and water, and occafion a 

 degree of opacity. Such fubftances alfo in their folid 

 ftate as confift of a mixture of gum and refin are al- 

 ways opake, while the pure gums and pure refins have 

 more or lefs of tranfparency. 



Gum is very abundant in the vegetable kingdom ; 

 it is found in a great number of roots - 3 the young 

 Ihoots and young leaves contain it in large quantities, 

 and its prefence may be known by ics vifcous and ad- 

 hefive quality, when thefe parts are crufhed between 

 the ringers. Gum is ufually obtained by wounding 

 6 the 



