222 ANATOMY OF VERTEBRATES. 



moved in tlie direction of ' retraction,' as the limbs hang in fig. 140, 

 tlie 'flexors ' of the fingers have their homotypes in the hind limb 

 called ' flexors of the toes,' and the mnscles effecting the opposite 

 movements of the digits are termed ' extensors ' in both fore and 

 hind limbs. The muscle, 40, arising from the fascia of the knee, 

 becomes by its insertion the extensor longus digitorum pedis. 

 The muscle, 41, is the flexor longus digitorum pedis. A short 

 extensor arises from the fore part of the tarsus ; its tendons 

 unite with those of the long extensor. A short flexor from the 

 opposite side of the tarsus divides, to be inserted by fleshy filjres 

 into the tendons of the flexor longus. The hallux has a special 

 extensor and aljductor : the fifth toe has also an abductor : these 

 combining in action, enlarge the breadth of the foot. 



In the higher reptiles, of the order Crocodilia, chiefly affecting 

 the watery element, and with frame and limljs propcn-tioned 

 for natation, the ]irimitive segmental structure continues to 

 be shown by the vertical aponeuroses passing outward from each 

 successive vertelara, especially from the di- and plcur-ajiophyses ; 

 tlicy divide the mass of muscles answering to the caudal myo- 

 connnas of Fishes and fish-like Batrachia in the tail ; to the 

 spinalis dorsi, lone/issimus dorsi, and sacrolumhalis of higher Ver- 

 tel)rates in the back ; and to the cervicalis ascendens, spleniiis capitis, 

 and transversalis colli in the neck. The posterior attachment of 

 the sacrolurnixdis is to the fi)rc part of the ilium by a slender ten- 

 don : that of the longissimus dorsi is to the sacral ribs. External 

 to the lono'issimus dorsi is the tracltehimastoideus, oriirinatinsj 

 Ijchind from the diapophyses of the second or third dorsal vertebra, 

 passing forward between the di- and zyg-apophyses of the cer- 

 vical vertebras, deriving slips therefrom, and inserted into the 

 mastoid. The complexns rises from the sides of the neural spines 

 of the middle cervical vertebra, and is inserted into the parocci- 

 pital. The splenius capitis arises from the neiu'al spines of the 

 anterior dorsals, and is partly a continuation of the spinalis dorsi: 

 it is inserted into the superocci])ital, and shows traces of the seg- 

 mental structure. The powerful muscles of the tail are more 

 decidedly divided by aponeurotic septa into segments, correspond- 

 ing with the vertebra? ; but they are grouped together, by Cuvier, 

 into three pairs of longitudinal muscles. The first is neural in 

 position, and chiefly a liackward prolongation of the spinalis dorsi ; 

 the myocommal septa form an angle directed forward. The 

 second is lateral, and begins by a strong tendon from the upper and 

 back ])art of the ilium, and by a second tendon from the ischium : 

 It is also connected with fleshy flattened fasciculi from the pubis 



