52 PARA RUBBER, 



A fourth point, which has obviously received attention in the 

 knives recently put on the market, is that the instrument used for 

 re-opening or paring the lower surface of the wound should be so 

 constructed that only the minimum quantity of material is cut away 

 at each operation. The longevity of the tapping area depends upon 

 this operation, and at the present time there are knives which will 

 demolish 12 inches of hark in three months, and others which will not 

 use up the same quantity of tissue in two or three years. The very 

 narrow cutting margin of knife No. 2, shown on Plate 9, Series A, is 

 specialy devised for paring away very thin shavings of the bark. 



The introduction of pricking instruments for cutting the laticif- 

 erous tubes in the wound area, though duplicating the tools, is very 

 useful; generally the duplication of the tools required to make the 

 first and subsequent incisions is undesirable, and in several instru- 

 ments the power of adjustment is such as to allow all the operations 

 to be carried out by means of one knife only. 



Paring and Pricking. 



The amount of cortical or bark tissue which is cut away by one par- 

 ing operation is sometimes surprisingly large. The average cooly 

 will excise the lower surface until a large number of white globules of 

 latex have appeared, when by the use of other implements the latex 

 tubes might have been tapped without excising any cortical cells at 

 all. It has been asserted that since the most careful method 

 may only allow one to tap the whole of the surface from the base up 

 to six feet in two to three years, the care advocated is not necessary 

 when large acreages have to be tapped. But the necessity of tap- 

 ping every tree on a large plantation is no excuse for excising the 

 cortical tissues in a wasteful manner. The best results will follow 

 from those methods which involve the removal of the minimum 

 amount of cortical substance during tapping operations. 



It has been urged that even if one removes large quantities of 

 tissue when tapping, the rubber can still be extracted from the mate- 

 rial thus removed. This is correct especially when large quantities of 

 bark are cut away, but the greater part of the rubber can, by proper 

 paring and pricking, be removed without great waste of tissues. 



Furthermore, it should be distinctly borne in mind that the re- 

 moval of the cortical cells means the destruction of the living tissues 

 wherein the latex tubes arise. The actual quantity of rubber in the 

 cortex at any particular time is very small compared with that which 

 can be obtained by pricking the latex tubes, allowing them to 

 become refilled, and encouraging their development. 



Patent Tapping Knives. 



The native collectors of rubber in the uncultivated forests of Brazil 



use an axe-like implement, with which a heavy blow can be inflicted 



and all the tissues from the bark to the cambium be cut in one stroke. 



At the present time Ceylon is taking a very active interest in invent- 



