THE HEVEA RUBBER TREE IX THE AMAZON VALLEY 33 
dinho. The average daily yield of latex is considerably in excess of 
that obtained by Akers, who doubtless used more severe methods; 
but the yield shown in Table 1 is greatly in excess of that obtained 
by Akers with the machadinho in his experiments, so that the differ- 
ences may be set down as due to differences in the condition of the 
estradas/ Akers believed the yields in South America could be 
doubled by using the gouge or knife. This may be possible, though 
it is doubtful whether modern conservative tapping systems would 
give so great an increase, but there can be no doubt that a substan- 
tial increase would be obtained, though part of this advantage might 
be lost in a slightly increased cost of tapping. A trained tapper 
should be able to tap nearly as many trees with the knife as the 
ordinary seringueiro does with the ax. 
The writer inclines to the belief that oriental methods can be 
adapted to tapping on virgin trees with good results, but not on old 
tapped trees unless they have rested for a long time. The greatest 
difficulties lie in the training and control of the tappers. It is doubt- 
ful whether an old seringueiro can ever be trained to be careful of 
the bark of a tree, and unless care is exercised the knife may be even 
more terrible in its effects than the ax. At present an adequate 
system of control is practically impossible, so that for most estradas 
the gouge and the Jebong knife may be dismissed from consideration. 
The tool known as the Amazonas knife is very promising as a 
substitute for the ax. As usually made, it has a long handle and is 
provided with a cutting blade shaped like that of the Jebong knife, 
but with a smaller curve, so as to be adapted to use in thinner bark. 
It is complicated by an attachment designed to clean the blade or to 
regulate the thickness of the cut; the writer never knew for which 
use it was intended, and it is certainly equally worthless for either. 
The shank of the knife is provided, with a long extension, like the 
blade of a table knife. This was intended to serve as an instrument 
of incision after the knife had been used to excise a grooved cut to 
conduct the latex. The custom of using the knife in this way is 
indeed more honored in the breach than in the observance, for where- 
ever the knife penetrates the cambium it produces an excrescence, 
as might be expected. These excrescences are small and not very 
serious if a rather long time be allowed for bark renewal, but there is 
no need of producing them, and the knife is usually used only for 
excision and not for incision. Only at Seringal Miry, near Manaos, 
an experimental plantation in as good condition as any seen in South 
America, did the writer find the knife used for incision. 
In using this knife the bark is not pared away completely, as with 
the gouge or the Jebong knife, but a small portion of bark is left 
intact between each two cuts. The cuts do not run so deep as those 
made by the other tools; therefore the knife is better adapted to tap- 
ping the bark of old injured trees. It is also successful with thinner 
bark than can be tapped with the gouge or Jebong knife. Figure 
10 shows a tree which has been tapped with this knife. 
On old trees badly affected with excrescences this knife causes 
considerable injury to the cambium, but much less than the ax. 
In general, the bark seems to be readily renewed after its use, and 
fungous infection seems less likely to follow its use than that of the ax. 
96522°— 28 3 
