OF DIDELPHYS VIRGINIANA. 



133 



extensor brevis digitorum, still higher up to the knee. (See, however, foot note on page 130). 

 Instead of arising from the os calcis and being wholly a plantar muscle, as in man, this short 

 flexor arises fleshy from, and lies upon, the common tendon of the long flexor, an inch or 

 more above the heel. At the point in the sole where the long flexor tendon subdivides, this 

 one also splits, likewise into four tendons, that pass one to each of the four lesser toes. 

 The fasciculus going to the second toe is more or less distinct from the rest, and lies wholly 

 or in part upon the tendon of the flexor longus poUicis. These tendons are all excessively 

 delicate ; those going to the second or third toes are the longest ; fleshy fibres accompany 

 the tendons to the base of the fourth and fifth toes. Each tendon at the base of a toe 

 gives off on either side fascial expansions, that bind it to the common sheath of the toe, 

 and embrace the heavy tendon of the deep or long flexor. Further on, each tendon splits, 

 embracing again the deep tendon, and proceeds to be inserted into the base of the second 

 phalanx. The lumbricales appear to belong almost as much to this set of tendons as to the 

 deep ones. 



Flexor longus pollicis. — (Fig. 34, e, and h.) A small flat- 

 tened, fusiform muscle, arising from the head and outer aspect 

 of the shaft of the tibia, and the intermuscular septum between 

 itself and the tibialis posticus. Its long, slender, flattened ten- 

 don runs along the inner border of the tendon of the latter, 

 passes in a groove behind the extremity of the tibia, gaining 

 the sole of the foot, where it lies along the inner border of the 

 flexor longus digitorum. It does not, however, proceed to the 

 great toe, but is inserted into the tendons of the flexor longus 

 digitorum and flexor brevis obliquus pollicis, just where the two 

 latter become blended together. These three tendons thus fuse 

 at a common point. Nature seems to have repented of making 

 this animal's foot so much like a hand, and to have inconti- 

 nently tied the two flexor tendons of the great toe to the com- 

 mon tendon of the other toes, so that this opposable digit cannot have other independent 

 flexion than that afforded by the little muscles upon its ball. 



Tibialis posticus {extensor tarsi tibialis). — (Fig. 34,/, and fig. 35, c.) A small muscle 

 with a short belly, lying deep seated between the foregoing and the long digital flexor. It 

 arises from the inner part of the head of the fibula, contiguous part of shaft of tibia, and 

 intermuscular septum betwixt itself and the foregoing muscle. Its tendon, twice as long 

 as the fleshy part, passes behind the internal malleolus, on the tibial side of the flexor 

 longus digitorum, to be inserted into the inner side of the scajihoid. 



Interosseus cruris. {"Pronator Jibulce quadratics.")^ The interosseous space between 

 the bones of the leg is occupied, from knee to ankle, by a plane of obliquely transverse 

 fibres, situated between the two layers of the interosseous membrane. The direction of the 

 fibres decussates with that of the aponeurotic fibres ; and, particularly on the lower part 

 of the front of the leg, the aponeurosis is very strong, dense and glistening. Though the 

 muscle, as a matter of fact, cannot really pronate the limb, its action is in this direction ; 



Fig. 35.- 



'Prof. Owen (Comparative Anatomy and Physiology, iii, mimis;" and in the same animal he considers the muscle 



p. 15) says of this muscle, in the case of Dasi/urus macrurus, that sends flexor tendons to all the toes except the rudi- 



that it " may be the homologue of the flexor digitorum com- mental hallux, as the fle.\or longus pollicis. 



UEIUOIBS HOST. 60C. NAT. HIST. VOL. II. 34 



