THEORY OF THE EARTH. 91 



initiating animals, because the former have either 

 incisors, or canine teeth, and almost always both 

 in each jaw ; and the structure of their foot is in 

 general more complicated, because they have 

 more toes or claws, or their phalanges less enve- 

 loped in the hoof, or a greater number of dis- 

 tinct bones in the metacarpus and metatarsus or 

 more numerous tarsal bones or a fibula more 

 distinct from the tibia or, lastly, that all these 

 circumstances are often united in the same species 

 of animals. 



It is impossible to assign reasons for these rela- 

 tions ; but we are certain that they are not the 

 effects of chance, because, whenever a cloven-footed 

 animal manifests, in the arrangement of its teeth 

 some tendency to approach the animals we now 

 speak of, it also manifests a similar tendency in 

 the arrangement of its feet. Thus the camels, 

 which have canine teeth, and even two or four 

 incisors in the upper jaw, have an additional 

 bone in the tarsus, because their scaphoid bone is 

 not united to the cuboid, and they have very 

 small hoofs, with corresponding phalanges. The 

 musk animals, whose canine teeth are much de- 

 veloped, have a distinct fibula along the whole 

 length of their tibia ; while the other cloven-foot- 

 ed animals have only, in place of a fibula, a small 

 bone articulated at the lower end of the tibia. 

 There is, therefore, a constant harmony between 

 two organs apparently having no connection ; and 



