LOST DURABLE OF AXIMAL SL'BSTAXCES. XI 



interesting to the physiologist. They form for the 

 same reason most important guides for the naturalist 

 in the classification of animals; and their value, as 

 zoological characters, is enhanced by the facihty with 

 which, from their position, they can be examined in 

 living or recent animals. The durability of their tis- 

 sues renders them not less available to the paleontolo- 

 gist in the determination of the nature and affinities 

 of extinct species, of whose organization they are often 

 the sole remains discoverable in the deposits of former 

 pen'ods of the earth's history." 



Prof. A. Chanveau says ("Comparative Anatomy of 

 the Domesticated Animals"): 



" Identical in all our domesticated animals by their 

 general disposition, mode of development, and struc- 

 ture, in their external conformation the teeth present 

 notable differences, the study of which offers the 

 greatest interest to the naturalist. For it is on the 

 form of its teeth that an animal depends for its mode 

 of alimentatioii; it is the regime, in its turn, which 

 dominates the instincts, and commands the diverse 

 modifications in the apparatus of the economy; and 

 there results from this law of harmony so striking a 

 correlation between the arrangement of the teeth and 

 the conformation of the other organs, that an anato- 

 mist may truly say, 'Give me the tooth of an animal, 

 and I will tell you its habits and structure.'" 



In a letter which I wrote to Prof. Theodore Gill, of 

 the Smithsonian Institution, Washington, D. C., I 

 asked what there was about teeth that enabled natu- 

 ralists to tell so much bv them. In reply he said: 



