524 Opposable Power of the Thumb, 



so nearly to the quadrumanous as this does to the pedima- 

 nous, but that the whole three form so many constituent and 

 subordinate groups of the same natural order, and are united 

 by a chain of affinities too strong to be arbitrarily dissevered. 

 At the same time, the Bimana have peculiar and appropriate 

 characters, which, even in a physical point of view, exalt 

 them sensibly above the allied families. The very separation 

 of the functions of locomotion and prehension, and their 

 appropriation to different organs, gives man a notable supe- 

 riority over all other mammals; for by this means the organs 

 of touch and prehension preserve their delicate and sensitive 

 structure unimpaired by contact with the hard and rough 

 ground. They are, besides, resident in that pair of the extre- 

 mities which is situated in the immediate vicinity of the organs 

 of sense and mind, and thus in the most convenient situation 

 possible for executing all the various commands of the will ; 

 whilst the erect station of the body, and the appropriation of 

 the function of locomotion to the posterior extremities alone, 

 prevents them from being interfered with in the execution of 

 these essential duties. The Quadrumana, on the contrary, 

 continually obliged to employ the anterior as well as the pos- 

 terior extremities in the act of progression, have the sense of 

 touch and power of prehension seriously diminished in con- 

 sequence; whilst the Pedimana, with the proper organs of 

 prehension upon the posterior extremities only, are placed in 

 still more unfavourable circumstances with regard to the faci- 

 lity of executing these functions, or obeying the commands of 

 volition. In fact, the hind thumb in pedimanous and qua- 

 drumanous mammals is manifestly designed for no other 

 purpose than to assist the function of locomotion, by giving 

 those animals a more perfect power of prehension in grasping 

 the branches of the trees among which they habitually reside ; 

 but the Quadrumana have the farther advantage of anterior 

 hands, which the Pedimana do not possess, which adapt them 

 to still more important acts of prehension, and approximate 

 them more closely to the human type. They consequently 

 occupy an intermediate position between the Bimana and Pe- 

 dimana, with which they are connected by means of the real 

 Apes (Pithecus) on the one hand, and of the Simiadaa of 

 South America on the other. The entire group thus presents 

 a beautiful gradation of zoological characters from man to the 

 Simias, and from those to the Sapajous, Sagoins, and Opos- 

 sums, and an uninterrupted chain of the most important 

 affinities, which clearly vindicate its right to be considered as 

 a strictly natural family of mammals ; whilst the important 



