METHODS OF INJECTION. 



665 



vat d, with a pressure due to its height above the ground, is 

 therefore driven into the log and expels most of the sap, which 

 issues from the smaller end of the log, at first pure hut eventually 

 mixed with the injecting solution. This waste liquid flows into 

 a wooden trough s, and is then conducted to the tank K, which 

 is provided with a filter to exclude impurities [and also a basket 

 full of crystals of the injecting substance in order to maintain the 

 strength of the solution. — Tr.] The liquid in K is then pumped 

 back into the vat h by the pump iv. Instead of forming the 



Fm. 296. 



hollow space at the base of the log by means of a piece of rope, 

 Oesau used a metallic vessel, like a round, shallow box, the sides 

 of which are sharpened so that they can be driven into the base 

 of the log with a few blows of a hammer, whilst there is an 

 orifice in the base of the box into which the tube j) i« screwed. 



[Boppe states that long logs in France are injected by being sawn 

 nearly across at their middle (fig. 297), so that a thickness of only 

 li to 2 inches of wood is left below, the log is then raised by levers 

 and a piece of rope inserted in the opening. On removing the levers, 

 the log returns to its former position, and the cut closes tightly on 

 the rope ; an augur-hole is then bored obliquely through the log 

 into this hollow space, and the gutta-percha tube placed in it as 

 before.— Tr. J 



Wood to be thus injected should be freshly cut, and still full 

 of sap. Stems are therefoi-e topped, branches cut down to short 



