THE SURFACE OF THE GLOBE. 63 



whence we may account for the absence of the clavicle and the acro- 

 mion, and the straightness of the scapula ; not having any occasion to 

 turn the fore-leg, their radius will be solidly united to the cubitus, or 

 at least articulated by a hinge-joint, and not by ball and socket, with 

 the shoulder ; their herbaceous diet will require teeth with a broad 

 surface, to crush seeds and herbs ; this breadth must be irregular, and 

 for this reason the enamelled parts must alternate with the osseous 

 parts ; this sort of surface compelling horizontal motion, for grinding 

 the food to pieces, the articulation of the jaw cannot form a hinge so 

 close as in carnivorous animals ; it must be flattened, and correspond 

 with the facing of the temporal bones, more or less flattened ; the 

 temporal cavity, which will only contain a very small muscle, will be 

 small and shallow, &c. All these are necessary deductions one from 

 another, according to their greater or lesser universality ; and so that 

 some are essential and exclusively belonging to hoofed animals, and 

 others, although equally necessary to those animals, are not peculiar 

 to them, but are to be found in other animals, where the other general 

 rules of structure admit of these also. 



If we descend to the orders or subdivisions of the class of hoofed 

 animals, and examine what modifications the general condition un- 

 dergo, or rather, what peculiar conditions are united to them, accord- 

 ing to the character proper to each of these orders, the reasons of 

 these secondary conditions begin to appear less palpable. We soon 

 perceive, in general terms, the necessity of a digestive system more 

 complicated in the species where the dental system is more imperfect ; 

 thus we might say that these should rather be ruminating animals, 

 where such and such an order of the teeth is wanting ; we may de- 

 duce from it a certain form of the oesophagus, and corresponding for- 

 mation of the vertebrae, of the teeth, &c. But I doubt whether any 

 one would have guessed, if observation had not suggested it, that 

 ruminating animals would all have cloven feet, and that they alone 

 would have them : I doubt whether any one would have guessed that 

 those only would have horns on the forehead that belong to this class ; 

 that those amongst them who have sharp eye-teeth are for the greatest 

 part deficient in horns, &c. 



However, since these coincidences are constant, they must have a 

 satisfactory cause ; but as we do not know it, we ought to supply the 

 defect of the theory by observation • it serves us to establish supposi- 

 tious laws, which become almost as certain as the laws of reasoning, 

 when they rest on often-repeated observations ; so that now, any one 

 who sees the track of a cleft-foot may conclude that the animal who 

 left it is ruminant ; and this assertion is as sure as any other in physics 

 or morality. This foot-mark alone gives to the observer both the 



