240 Dr Maclagan on Gutta Percha. 



chouc oil, and in ether. It is insoluble in alcohol and in 

 water, and floats upon the latter. 



Its most remarkable and distinctive peculiarity is the ef- 

 fect of heat upon it. When placed in water at 110", no effect 

 is produced upon it, except that it receives the impression of 

 the nail more readily ; but when the temperature is raised to 

 145° or upwards, it gradually becomes so soft and pliant as 

 to be capable of being moulded into any form, or of being 

 rolled out into long pieces or flat plates. "When in the soft 

 state, it possesses all the elasticity of common India-rubber, 

 but it does not retain these properties long. It soon begins 

 again to grow hard, and a short time, varying according to 

 the temperature and the size of the piece operated on, re- 

 gains all its original hardness and rigidity. A ball one inch 

 in diameter was completely softened by boiling water in ten 

 minutes, and regained its hardness completely in less than 

 half an hour. It appears to be capable of undergoing this 

 alternate softening and hardening any number of times with- 

 out change of property. 



It is also to a certain extent ductile. When soft it is easily 

 torn across, but when hard it is very tenacious. A piece not 

 an eighth of an inch in thickness, when cold, easily raised a 

 weight of foi*ty-two pounds, and only broke when half a 

 hundred weight was attached to it. 



From these properties, it seems capable of many applica- 

 tions in the arts. Its solution appears to be as well adapted 

 as that of common caoutchouc for making waterproof cloth, 

 and, whilst softened, it can be made into solid articles, such 

 as knife-handles, door-handles, &c. The Malays employ it for 

 the former of these, and prefer it to wood. A surgeon, fur- 

 nished with a small piece, could easily, with the aid of a little 

 hot water, supply himself with bougies or pessaries of any 

 size or form. 



[Dr M. exhibited a knife-handle, a walking-cane head, a 

 riding-whip, and (-ther articles, made of gutta percha.] 



