308 ELEMENTARY ANATOMY. [LESS. 



The abductor pollicis pedis takes origin from the cuboides 

 and third and fourth metatarsals. Passing obliquely, it is 

 inserted conjointly with the external insertion of the flexor 

 brevis pollicis. 



The transversus pedis is a narrow band stretching from 

 the distal ends of the metatarsals and blending with the 

 insertion of the adductor pollicis into the first phalanx of the 

 hallux. 



The interosseous muscles are like those of the hand, except 

 that it is the second digit, not the third, which has two dorsal 

 interossei. This condition results simply from the fact that 

 the origin (from the metatarsal) of the fibular interosseus of 

 the second digit is placed on the dorsal side of the tibial 

 interosseus of the middle digit. 



Such is the norm il condition of man's muscles, but these 

 structures are liable to considerable individual variation. 



15. On turning to other Vertebrate animals in order to 

 estimate the peculiarity of man's muscular structure, we find 

 that, as regards the MUSCLES OF THE HEAD AND NECK, 

 the occipito-frontalis truly belongs to a distinct category of 

 " skin -muscles," whereof the platysma myoides also forms a 

 part. This dermal group of muscles is very feebly repre- 

 sented in man compared with what we find in brutes, e.g. 

 the Horse, where it is termed the panniculus carnosus, and 

 by its contractions produces those twitchings of the skin 

 which must be familiar to most readers. It is most de- 

 veloped in such forms as the Porpoise (where it envelops the 

 whole body from the occiput to the tail end), the Echidna, 

 and the Hedgehog. In the last-named animal it is so com- 

 plex that it may be divided into nine pairs of muscles, one 

 pair being the " occipito-frontalis." When all these muscles 

 contract, the animal becomes " rolled up," the limbs be- 

 coming, as it were, enclosed in a muscular bag. The panni- 

 culus is commonly inserted into the arm and leg, and part 

 of it may, as in the Echidna, be applied round the mammary 

 gland, which it serves to compress. 



Muscles such as those which exist in man's face may be 

 wanting altogether, as e.g. in the Tortoises, but some of them 

 may, as we shall see, be much more developed in certain 

 animals than they are in him. 



Thus we may have his superior auricular represented by 

 two muscles, and his anterior auricular and his posterior 

 auricular by four, together with two or three extra muscles, 

 as in the Horse. 



