336 ELEMENTARY ANATOMY. [LESS. 



The muscle may be double and very voluminous, as e.g. in the 

 Chameleon. Even in very near allies of man (the Anthropoid 

 Apes) it ends in two tendons, one going to the trapezium, the 

 other to the metacarpal of the thumb. 



The extensor primi internodii pollicis appears to be exclu- 

 sively human. 



The extensor secundi internodii pollicis is often wanting. 

 It may coalesce with the extensor indicis, as in the Dog and 

 Rabbit. 



Extensor indicis. This muscle may be absent as well as 

 that last described, as e.g. in Hyrax. It may send tendons to 

 other muscles besides the index, viz. to the third, fourth, or 

 fifth digits, as in the Lemuroidea. 



Supinator brevis. This may even in Mammals be entirely 

 absent, as in the Horse. There may however be an acces- 

 sory supinator, as in the Iguana. 



22. The MUSCLES OF THE HAND of man of course possess 

 an especial character in harmony with the special perfection 

 of that organ in him. Its muscles, with the exception of the 

 interossei, can hardly be compared with any profit with the 

 muscles of creatures below the rank of Mammals. For 

 though sometimes (as e.g. in Chameleo) we may meet with a 

 so-calledy&?.r0r brevis pollicis or fiexor brevis minimi digiti, 

 it is difficult to assert that these are really homologues of the 

 muscles so named in man. Nevertheless, though the muscu- 

 lar condition of the human hand is special, yet its essential 

 type is that common to the class to which man belongs, and 

 especially like that of his own order, Primates, the members 

 of which possess all the manual muscles of man, only more 

 or less different in form and proportion. It may be, how- 

 ever, that these muscles are wanting altogether, as in the 

 Horse and Whale, but they are generally present even where 

 they might not be expected (at least all), as e.g. in the Dog. 



Opponens pollicis. This muscle in man attains its maxi- 

 mum degree of relative size. It is not only present, though 

 small, in the Primates generally, but it is present in forms 

 quite destitute of an opposable thumb, as e.g. in the Dog. 



The adductor pollicis may be inserted into the index 

 through atrophy of the pollex, as e.g. in the Dog. 



Palm.iris brevis. This muscle is not peculiar to man. It 

 not only exists in his order, as e.g. in Lemur, but is found 

 even in Marsupials, e.g. the Tasmanian Devil. In the 

 Echidna it has been said to take origin from the ulna. 



Opponens digiti minimi. This muscle exists not only in 



