344 THE MECHANICAL TUNCTIONS. 



Animals, like the hare, in which, from the great length 

 of the hinder limbs, the posterior half of the body is higher 

 than the anterior, run much better up a declivity than on 

 level ground. In a descent, on the contrary, they are 

 obliged to pursue an oblique and zig-zag course, otherwise 

 they would be in danger of oversetting, as happens occa- 

 sionally to the Agouti and the Guinea pig^ when these ani- 

 mals attempt to run down hill. 



The Sloth, which is formed for clinging with great tena- 

 city to the boughs of trees, presents a remarkable contrast 

 to the animals we have just noticed; its fore legs being much 

 longer than the hinder, and its movements being proverbi- 

 ally slow. The peculiar modifications of its muscular powers 

 are probably consequences of the singular mode in which, 

 as I shall afterwards have occasion to notice, its arteries are 

 distributed. 



The Camcleopard^ likewise, has the fore legs much longer 

 than the hinder. The object of this conformation was pro- 

 bably to elevate the anterior part of the spine, so as to raise 

 the head as much as possible, and also to give a considera- 

 ble inclination to the whole column, for the purpose of dis- 

 tributing more equally the weight of the head and of the 

 very long neck upon all the legs; for the length of the neck 

 is fully equal to that of the trunk. It is evident that if the 

 body had been placed in the usual horizontal position, the 

 anterior extremities would have had to support the whole 

 of the enormous weight of this neck and head. This pecu- 

 liarity of structure, however, introduces considerable modi- 

 fications in the mode of progression of the animal. The 

 ordinary pace of the cameleopard is the amble; but it has 

 also a slower walking pace, and occasionally a gallop. In 

 the amble, its undulation is so considerable as to give it the 

 appearance of being lame. A similar kind of limping gait, 

 arising from the same cause, namely, the disproportionate 

 elevation of the fore part of the spine, has been observed in 

 the Hyena, 



