220 Proceedings Columbia Biochemical Association [March, 



a light, wine-red, tint, then to a dense brick-red precipitate, which 

 suffuses the volume of the liquid. A 0.02 percent sol. of glucose 

 causes fair reduction; in o.oi percent sol, reduction is slight though 

 perceptible. Sol. to be tested must be alkalin, and must not contain 

 potassium Cyanid or oxidizing agents (e. g., free Halogen, hydrogen 

 peroxid, potassium permanganate, potassium bichromate). Sugar- 

 free urine gives a positive reaction when it is acidified with hydro- 

 chloric acid. This positive reaction is probably due to acetone sub- 

 stances and Creatinin, which reduce acidified sol. of sodium selenite. 



Minute amounts of selenium, in the form of selenite ion, can be 

 detected by a procedure similar to that of the Marsh test for arsenic. 

 One mg. of selenium dioxid yields a characteristic dull red mirror, 

 soluble in oxidizing agents. 



167. A further study of the effects of acid media on natural 

 extracted teeth. Alfred P. Lothrop and William J. Gies^ 

 with the collaboration of Henry W. Gillett, Charles C. Linton, 

 Arthur H. Merritt and Herbert L. Wheeler.^® The fermen- 

 tation of glucose on normal and filled teeth, with sound enamel 

 " worn very little or not at all," in the presence of saliva, induced 

 rapid decalcification of the enamel and speedy disintegration of 

 some of the Allings. These effects were more pronounced on sali- 

 vated teeth covered with muslin than on similarly salivated teeth 

 that were not thus covered. 



Two daily brushings, for 4 months with tap water, and con- 

 tinuous daily treatment under muslin Covers, during the intervening 

 periods, with (a) water, (b) water containing carbon dioxid, and 

 (c) water holding an abundance of salivary mucin (mucin not muci- 

 nate), failed to induce injurious effects on teeth with sound enamel 

 " worn through and exposing dentin," and with enamel " worn very 

 little or not at all." 



Two daily brushings, for 4 months with tap water, and con- 

 tinuous daily treatment under muslin Covers during the intervening 

 periods, with (a) 0.25 percent Solution of mono-sodium di-hydrogen 

 phosphate (NaH2P04), and with (b) aqueous Suspension of sahv- 

 ary mucin (not mucinate) plus 0.25 percent Solution of mono- 

 sodium di-hydrogen phosphate, failed to induce injurious effects on 

 either the enamel or the fillings in teeth having sound enamel that 



^^ Journal of the Allied Dental Societies, 1914, ix, p. 554. 



