COLOPHONY 455 



of oleo-resin ducts are formed, from which abundant oleo resin is 

 poured out over the wound ; after a time this formation of ducts and 

 discharge of oleo-resin diminishes, and eventually ceases, but may 

 be continued by repeating the injury which caused their production. 

 The flow may therefore be continued for some considerable time. 

 Hence the oleo-resin is not a normal (' physiological ') but an abnormal 

 (' pathological ') product. 



The term * common ' turpentine is practically restricted to the 

 oleo-resin obtained in America, as the English market is almost 

 exclusively supplied from that source. The bulk is obtained from 

 Pinus palustris, Miller, the long-leaf pine, but P. Tceda, Linne, the 

 loblolly pine, P. eckinata, Miller, the short-leaf pine, and P. cubensis, 

 Grisebach, the Cuban pine, all yield a considerable quantity. These 

 trees, especially the long-leaf pine, form extensive forests in the 

 southern and south-eastern United States, extending from Texas to 

 North Carolina. 



The oleo-resin is collected in the following manner : 



In the winter, when no oleo-resin flows, cavities are cut in the 

 trunk of the tree near the base ; they slope inwards and downwards, 

 and are destined to receive the turpentine. In the spring triangular 

 incisions are made above the cavity or ' box,' the bark and part of 

 the young wood being removed. The turpentine soon rapidly exudes 

 and collects in the box, from which it is removed by a dipper. After 

 eight or ten days the flow diminishes , but may be increased by cutting 

 a strip of bark above the triangular incision ; this process of hacking 

 is repeated until the autumn, when the flow of turpentine gradually 

 ceases. The last portions that are slowly exuded partially dry before 

 they reach the box, and form a white incrustation on the hacked 

 surface. This incrustation is removed and forms the drug known in 

 America as 'scrape,' and in England as ' gum thus' or 'American' 

 or ' common ' frankincense. 



The crude turpentine is removed by a dipper from the boxes to 

 barrels for transportation to the stills. These are of copper, and set 

 in brick furnaces. Water is added and the whole warmed, any chips 

 of wood, &c., that float to the top being skimmed off. The head 

 is then luted on, and the heat increased. At first, water and oil of 

 turpentine distil over, subsequently oil of turpentine alone. Water 

 is occasionally added to prevent the resin from charring. After the 

 distillation has been stopped the melted resin is run through wire 

 strainers into barrels. 



The finest resin is that obtained from the tree in the first year, 

 when the crude turpentine yields about 80 per cent, of it. After that 

 the proportion of oil of turpentine in the oleo-resin gradually diminishes, 

 whilst that of the resin increases, but the latter become darker and 

 darker in colour. Tschirch has shown that the yield of turpentine 

 is greatly increased if the trees are wounded before the spring. 



