Gums, Resins, 



3 



[July, 1908. 



The "full-herringbone" system, which 

 has been used by the natives in Central 

 America and in Africa is a natural 

 development of the V incisions such as 

 those made in Mexico. The idea was 

 simply to connect the apices of the V's 

 by a longitudinal incision, the object of 

 which was to serve as a conduit for the 

 latex. The objection to this system is 

 the same as in regard to the V incision. 

 The oblique incision meeting at the apex 

 of the angle make a bad wound difficult 

 to heal. 



A modification of this last method is 

 the "half-herringbone" system. This 

 consists of a longitudinal channel, into 

 which the oblique cuts lead from one 

 side. Experiments have shown that this 

 method is the most practical and 

 eflicient. 



In regard to tapping Castilloa trees, 

 I would advise the employment of the 

 " half-herringbone " system in the follow- 

 ing manner: — A rather shallow vertical 

 channel is first opened from the height 

 to which it is intended to tap the tree. 

 At the bottom of this vertical incision 

 the collecting cup is attached to the 

 trunk in the manner already described. 

 The operator now makes an incision on 

 the left side of the vertical channel, at 

 an angle of 45° to this, and as close to 

 the base of the trunk as possible. This 

 incision should reach nearly to the 

 opposite side of the trunk. The plan is 

 to leave approximately two inches of bark 

 surface uncut between the end of the 

 incision and the second vertical channel 

 which will be opened opposite to the 

 first one at the next tapping of the tree. 

 When this second tapping is done the 

 oblique cuts are commenced at the same 

 distance, or at about two inches from the 

 first vertical channel. This leaves on 

 each side of the tree a narrow strip, two 

 inches wide, from the base to the top, 

 where the cortex has never been injured, 

 and the development of the tree can go 

 on at all times without interruption. 



Having made the first cut as described, 

 the operator makes another oblique in- 

 cision about 12-18 inches above the first 

 one, and subsequently opens other in- 

 cisions at the same distance as high up 

 on the trunk as he can reach. About 

 two months later, when the incisions 

 made at the first tapping have healed, 

 the second series of incisions on the 

 opposite side of the trunk is made. 

 Two months later, if the seasons permit, 

 a third tapping is done, and this time 

 the oblique incisions are opened immedi- 

 ately below the earlier ones, and as close 

 to these as possible. If this policy is 

 followed out the surface of the trunk 

 will last for a number of years, and re- 



tapping of the old wounds can safely be 

 done 8 or 9 years later. The advantage 

 of this system is that it permits a 

 symmetrical growth of the trunk, and 

 no loss of latex is caused by cutting into 

 or through old channels, which are likely 

 to conduct the latex in the wrong 

 direction. 



In tapping operations great care should 

 be taken in not wasting latex, which is 

 often the case at present. Every drop 

 of latex should be well taken care of, as 

 neglect in this regard will cause a con- 

 siderable loss. All cups and collecting 

 cans should be well washsd in cold water, 

 and this water used in the coagulation 

 process. 



Sometimes it happens that the latex 

 coagulates very rapidly, even before it 

 has been brought iu from the field. This 

 is especially the case with the latex from 

 young trees. Coagulation can be pre- 

 vented by adding a few drops of for- 

 maldehyde to each can. 



Coagulation Methods.— Many differ- 

 ent methodsare in use for the purpose of 

 preparing the latex for rubber. One of 

 the most primitive used by the Indians 

 is to leave the latex alone to coagulate 

 by the fermentation process which 

 ultimately takes place. Another one is 

 to expose the latex in thin layers to the 

 atmosphere allowing evaporation of the 

 moisture. This leaves a black and very 

 sticky substance which easily deterio- 

 rates and becomes tacky. 



Another primitive method of the 

 Indians is to use an extract of a morning 

 glory wine, or Ipomeea bona nox, which 

 extract is added to the latex and quickly 

 causes coagulation. The rubber obtain- 

 ed in this way is fairly good, but rather 

 wet and irregular in appearance. 



Of more modern methods we have two 

 essentially different types— the chemical 

 and the mechanical. 



Coagulation is effected by means of 

 many different chemicals. 1 have made 

 experiments, several hundreds in num- 

 ber, using different memicals. The re- 

 sults vary greatly, and I cannot here go 

 into details, but can only mention that 

 the observations made in this connection 

 will soon be published. So much has 

 been established, that whatever chemical 

 is used the resulting rubber is not of as 

 good quality, as when coagulation is 

 effected by mechanical means. Chemi- 

 cally coagulated rubber is usually shorter 

 in fibre, and does not last as long as 

 mechanically prepared rubber. Some- 

 times it may be found necessary to use a 

 chemical coagulant, but wherever this 

 can be prevented we get a better rubber, 



