9] VITAL IMPORTANCE TO MANKIND 273 



gums, though usually tapping is necessary to obtain them in com- 

 mercial quantities, or they may be collected in the fossil state. For 

 the most part they are forest products. Some of the more valuable, 

 with their uses, are (i) the various copals, utilized as varnishes and 

 in making paints and linoleum; (2) amber, a fossil resin particularly 

 from an extinct species of Pine, which is used for beads, ornamental 

 carvings, and mouth-pieces of pipes, etc.; (3) damars, used princip- 

 ally in varnishes; (4) lacquer, a natural varnish which hardens on 

 exposure to air and affords remarkable protection even against acids 

 and alkalis; (5) shellac, excreted by a particular insect on twigs of 

 certain trees on which it feeds, widely used in insulation and decora- 

 tion and for making varnishes, sealing-wax, size, drawing inks, 

 gramophone records, and many other products ; and (6) turpen- 

 tines, chieflv obtained by tapping coniferous trees and yielding on 

 distillation oil of turpentine and rosin. Oil of turpentine is of major 

 importance in the paint and varnish industry as a solvent and thinning 

 agent, and in chemical manufacture, while rosin is the chief sizing 

 material for paper and is also used in many manufactures as well as 

 in greases and lubricants. 



Other noteworthy products in this general category include Canada 

 balsam, used in mounting microscope slides and as a cement for 

 lenses ; spruce gum, used as a masticatory ; Venetian turpentine, 

 used in varnishes and veterinary work ; and various balsams, used 

 in medicine, adhesives, soaps, lotions, and cosmetics, as well as for 

 the flavouring of foods and as fixatives in the perfume industry. 

 There are also such products as ammoniacum, used in medicine 

 and perfumery ; asafoetida, widely used in medical treatment ; 

 copaiba, used for making varnishes and lacquers, as a fixative of 

 perfumes in soap, and in photography and medicine ; elemi, used 

 in various artistic, cosmetic, and medical operations ; frankincense 

 used in incense, cosmetics, and fumigation ; and myrrh, used for 

 cosmetic and medicinal purposes as well as in incense and embalming. 



Tanning and Dyeing Materials 



Tanning involves the reaction of strongly astringent tannins with 

 such proteins as are present in animal skins, thus forming the strong 

 and resistant, flexible commodity we know as leather. Although 

 tannins are very widespread in plants, relatively few species are 

 known to contain a sufficient proportion to be of commercial import- 

 ance, and these are in great demand. The sources occur mostly 



