316 THE ANATOMY OF VERTEBRATED ANIMALS. 



fibula and tlie interosseous ligament, and its broad tendon 

 passes into the sole and coalesces with the tendon of the 

 smaller ^exor longus dlgitoruni. The conjoined tendons divide 

 into four slips — two large, median, and two small, inner and 

 outer. These go to the distal phalanges and sesamoids of the 

 respective digits. 



The tibialis 2^ostlGus is absent, but there is a small tihialis 

 anticus, 



A very complicated muscle represents the extensor longus 

 digitorum and i\iQ perojimus tertius. It arises by {a) a strong 

 round tendon from the outer condyle of the femur, just in fi'ont 

 of the external lateral ligament. From this tendon proceed 

 two fleshy bellies, one of which supplies tendons to the third, 

 fourth, and fifth digits, while the other ends in a broad band 

 of tendinous fibres, which is inserted into the third metatarsal 

 and the ectocuneiforra. Into this band is inserted {h) the 

 second fleshy head which arises from the upper part of the 

 tibia; and it is traversed by the tendon of (c) the third head, 

 which is slender, arises from the fibula, and sends its long and 

 delicate tendon to the dorsum of the second digit. 



The ^9ero/iOBW5 longus is present, and its tendon is inserted 

 into the entocuneiform and the second metatarsal. There is 

 no 2^S7^07iceus brevis. Kperonmus Aii et 6ti digiti arises from 

 the upper part of the fibula, behind \ihe, peronmus longus^ and 

 ends in a tendon which passes behind, and on the inner side 

 of, that of the latter muscle, to the dorsum of the foot, where 

 it divides into two branches which join the extensor sheaths 

 of the fourth and fifth dio-its. 



The extensor hrevis goes to the two middle digits, and is 

 connected with the middle tendon of the extensor longus. 



The interossei are similar to those of the manus. 



The formula of the milk dentition of the Pig (which is com- 

 plete at the third month after birth) is d.i. |^ d.c. ]^ d.m. \~' 



The outer upper incisors are directed obliquely outward 

 and backward. In the upper jaw, the anterior two molars 

 present sharp longitudinal edges, while the posterior two 

 have broad crowns with two transverse ridi^es. In the man- 

 dible the anterior three molars have sharp longitudinal edges, 

 while the hindermost has a broad, three-rid g-ed crown. 



The first permanent molar is the first tooth of the per- 

 manent set which comes into place (at about six months after 

 birth), and the permanent dentition is completed in the third 



