416 TRANSACTIONS OF THE AMERICAN INSTITUTE, 



fore unfit to form the basis for artificial teeth. Platina is not 

 subject to this objection, as acids do not oxydate it, still it pro- 

 duces a metallic taste in the mouth which irritates the salivary 

 glands and injures digestion. 



Metals are admirable conductors of heat, and often cause a 

 disagreeable sensation when hot food enters the mouth, or cold 

 air comes suddenly in contact with them. 



Then again the specific gravity of metals renders them unfit 

 for the purposes of dentistry. Platina is exceedingly heavy, and 

 very flexible, which overbalances, to a certain extent, its non-oxy- 

 dation qualities. 



What we require is some tasteless composition, that will not 

 excite the glands, create a disagreeable sensation in the mouth, 

 or emit odor. It must be a bad conductor of heat, not liable to 

 solution, corrosion or oxydation, by the action of the gastric 

 juice of the stomach, and capable of bearing any degree of heat 

 and cold. It must not be liable to bend, or get out of shape, and 

 must hold the teeth without cement or solder ; to accomplish this 

 end, the composition will necessarily have to be soft and pliable 

 when the teeth are united with it, and become hard and compact 

 afterwards. And as the gums always shrink after the loss of 

 natural teeth, the composition must be such as to imitate real 

 gums, be light, capable of plastic formation, and easily fitted 

 without clasps. AVhen this desideratum is acquired, the alveolar 

 sockets may be deprived of their dead roots, inflammation of the 

 jaws, swelling of the face, and irritation of the nerves entirely 

 dispensed with, and the constituent parts of our systems would 

 soon harmonize perfectly with this new and pure body. 



GAS BURNING. 



Prof. Hedrick. — Nitrogen dilutes gas and lessens the value of 

 it. Gas varies from day to day, and we scarcely ever burn Ihe 

 same kind of gas. Hydro and carbon is the general illuminating 

 gas that Ave burn, and the more carbon it contains the better it 

 is. Gas always contains free hydrogen, but if it has enough of 

 carbon in it it will give a good light. What is called the de- 

 fiant gas, is the best burning gas that we have. 



The Chairman stated that he was informed at the Manhattan 

 Gas Company, that gas traversing a length of pipe, say one and a 

 half miles, produced what is called vegetable decomposition. He 



