PKEHENSIOX OF FOOD. 231 



gather food. In the higher animals we find prehensile organs represented 

 in lower animals by special organs which in different species form a 

 single type of prehensile organ. Thus: in lower forms of life we have 

 tentacles, or the lip may serve as the chief organ of prehension, or the 

 tongue or the jaws ; while in the higher mammals we find all these 

 organs together serving the purpose of conveying food to the mouth. 



In the latter, which are of the same prehensile type as man, the 

 radius and ulna are isolated and movable, one on the other, and there 

 are distinct fingers, nails, or claws, as in monkeys, carnivora, and most 

 rodents. In all animals which use the fore limbs as prehensile organs, 

 this separation of the radius and ulna is invariabty to be found. In 

 the large mammals the anterior limbs are only for support, and such 

 animals are usually herbivorous. In them the radius constitutes the 

 principal bone of the forearm, while the ulna is very small and almost 

 always fused with the radius ; so no motion between the two is possible. 

 There are, however, numerous exceptions to this, and in animals where 

 it would be least expected. For instance : in the elephant the volume of 

 the ulna is superior to that of the radius, and its carpal extremity is 

 greater than that of the radius, and both are distinct. This also is the 

 case in the rhinoceros ; but in both these animals the motions of pro- 

 nation and supination are impossible. Most of the herbivora have a 

 forearm terminating in one or two single fingers or phalanges surrounded 

 by a hoof, and in these the radius constitutes the main or sole bone of 

 the fore extremit}'. The development of the ulna and the fingers are in 

 direct ratio. 



In the domestic animals the prehension of food is accomplished by 

 different organs, which have different degrees of usefulness and develop- 

 ment in different types. In the dog and cat the fore limbs have inde- 

 pendent radii and ulnae, a certain amount of pronation and supination is 

 possible, and they indicate, to a certain extent, the prehensile power of 

 the hand as seen in man and monkeys. Where, as in the herbivorous 

 quadrupeds, the fore limbs are destined solely for support and progression, 

 a long neck and peculiarly shaped head favor the use of the tongue, lips, 

 and teeth, which in these animals are the sole prehensile organs. The 

 tongue and lips are supplied with muscular tissue : hence the power of 

 motion. 



In the horse the upper lip is the principal organ of prehension. 

 This organ is supplied with circular muscular fibres, as well as ele- 

 vator and depressor muscles, the elevator being especially efficient in 

 curling and elevating the upper lip so as to grasp food. The elevator 

 of the upper lip terminates in a broad Y-shaped tendon, which is inserted 

 in the free part of the upper lip (Fig. 81). The tongue has extrinsic 

 and intrinsic muscles, which favor its protrusion and enable it to grasp 



