ABOUT CARPENTERS. 



233 



motion of the jaw prevails in the rodents. Other mammals have the 

 lateral motion in a great degree, making three motions. All verte- 

 brates have the jaws opening vertically, while articulates have hori- 

 zontal jaws, and the sea-urchin has converging jaws. 



Fig. 11. Molar Tooth of Mammoth (Elephas primigenius): a, grinding surface; b, side-view. 



The harmony and mutual dependence between all parts of an ani- 

 mal's body are not better shown than in the adaptation of the teeth of 

 vertebrates to the kind of food, and their consequent agreement with 

 the habits, structure, and form of the individual. A single tooth fre- 

 'quently reveals the entire character of its possessor. Indeed, no single 

 organ is of greater zoological value. Not only does the student of liv- 

 ing forms use the teeth as indicative of character and a means of clas- 

 sification, but their superior durability makes them of the very greatest 

 importance in the study of ancient life. 



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ABOUT CAKPENTERS. 



By MAURICE MAUEIS. 



IT is characteristic of architecture that the further back we look to- 

 ward the primitive state of man, the more the use of wood prevails 

 over that of stone, brick, and all other building materials, and the more 

 does the importance of carpentry exceed that of masonry. The condi- 

 tion of this art might well be taken as the basis of division between 

 the various stages of the civilization of a country. During the first 

 stage, wood is everywhere the only material used in construction ; the 

 second stage is marked by a mixture of wood and ashlar work ; while 

 in the third, or highest stage, carpentry yields constantly to mason- 

 work, until it becomes a mere subordinate agent. 



