NOVKMBEB 22, 1895.] 



■SCIENGE. 



687 



pound crowns of this type are formed by 

 the concrescence of three separate denticles. 

 Dr. Carl Eose has also completed a most 

 valuable investigation upon the causes of 

 the decay of teeth. (' Ueber die Zahnverderh- 

 niss in den Volksschiden.') With the aid of 

 two colleagues, in the schools of Freiburg 

 and the Black Forest he has examined 7,364 

 children and 179,087 teeth. Special objects 

 of the investigation were the relations of den- 

 tal caries to the geology of the country, and 

 the presence of a greater or less amount of 

 lime salts in the water, and, secondly, the 

 influences of the consumption of different 

 kinds' of farinaceous food. In general the 

 use of water or food poor in lime salts af- 

 fects the development of the teeth very un- 

 favorably ; and the use, especially, of fine 

 milled white bread is very prejudicial to 

 sound teeth, whereas the use of the com- 

 mon black bread keeps the teeth clean and 

 the gums in a healthy condition. As re- 

 gards stratigraphy the investigation shows 

 that as we pass from granitic to overlying 

 calcareous formations there is a steady de- 

 crease in the number of unsound teeth — 

 falling from 35.3 to 16.1%. These figures 

 are taken without regard to the character 

 of the bread and other food consumed by 

 the children and show exclusively the in- 

 fluence of water. The conclusion is that 

 the worst teeth of the calcareous districts 

 are always better than the very best teeth 

 found within the non-calcareous districts, 

 the degeneration of the teeth being indi- 

 cated by a yellowish white and bluish gray 

 color. 



In the matter of food, meat is a great 

 luxury among the peasant children, enjoyed, 

 if at all, only upon Sundays, and can be left 

 entirely out of account. Dr. Eose finds 

 that the consumption of the German 

 ' Kuchen ' (made of white flour with milk, 

 butter or oil and more or less sugar, raisins, 

 etc.) is very prejudicial to the teeth ; and, 

 in fact, the very worst teeth are regularly 



found within those districts where these 

 cakes are habitually consumed. The conclu- 

 sion as to food is that the very best form of 

 foods, so far as teeth are concerned, is the 

 black bread with its coarse, thick crust. 

 The investigation extends to the relation 

 between the general condition of the mouth 

 and gums and epidemics of diseases such as 

 diphtheria, which principally affect chil- 

 dren, and Dr. Eose maintains that there is 

 a direct relation between the unhealthy 

 condition of the teeth and gums and a pre- 

 disposition to epidemic diseases. He be- 

 lieves that in times of epidemics these dis- 

 ease germs are found in the mouths of 

 nearly all children and that a healthy con- 

 dition of the mouth resists the infectious 

 power of the germ. As regards sex, there 

 is very little difference between the boys 

 and girls in the matter of decay. It is an 

 interesting point that the development of 

 the teeth is very much more rapid in girls 

 than in boys, so that in children of the same 

 age a much larger proportion of milk teeth 

 are found among boys than among girls. 



The article closes with a strong appeal 

 for the education of children in the schools 

 in the proper care and protection of the 

 teeth, and the author recommends not only 

 the careful instruction of children in this 

 respect, but also the award of prizes. 



H. F. O. 



CUEEENT NOTES ON PHYSIOGRAPHY. 

 THE MARGINAL PLAIN OF CHINA. 



Skeetchly and Kingsmill describe ' the 

 loess and other superficial deposits of Shan- 

 tung, N"orth China ' (Quart. Journ. Geol. 

 Soc, London, li, 1895, 238-253), recogniz- 

 ing the alluvial delta plains of the great 

 rivers, a plain of marine sands, and a some- 

 what denuded lowland of loess. The 

 delta of the Yangtse is estimated to in- 

 crease by two square miles a year. The 

 sandy marine plain is broadly developed 

 over a bay-like area up the Yellow Eiver, 



