1867.] MYOLOGY OF IGUANA TUBERCULATA. 795 



Peroneus pritnus. This muscle (figs. 15, 16 & 18, P. 1) arises, by 

 a strong tendon, from the summit of the outer side of the external 

 condyle of the femur. Passing downwards, it becomes tendinous 

 just below the outer malleolus, and ends in a tendon which is in- 

 serted into the peroneal border of the fifth metatarsal bone, a little 

 above its middle. Behind the ankle its tendon expands into a broad, 

 strong, ligamentous fascia, which binds down the flexor muscles, 

 being attached internally to the internal margin of the hinder sur- 

 face of the astragalus. 



Peroneus secundus. A muscle, somewhat larger than the prece- 

 ding (figs. 15 & 16, P. 2), arises from the antero-external surface of 

 the fibula for almost its entire length. It is inserted close above 

 the insertion of the preceding muscle. 



Gastrocnemius. Two distinct muscles compose the gastrocne- 

 mius : — 



(1) The first of these (figs. 13, 17 & 18, G.I.) arises from the 

 internal condyle of the femur, where it is closely connected with the 

 insertion of the first jtart of the semimembranosus, which embraces it. 

 It is also attached to the tibial margin of the tibia, close to the in- 

 sertion of the semitendinosus. Passing downwards, it soon receives a 

 strong tendon from the biceps, which tendon runs down just internal 

 to its outer border. At the ankle it becomes aponeurotic, and con- 

 stitutes the most superficial and external part of the plantar fascia. 



(2) The second head (figs. 13, 15 & 18, G. E.) arises from the 

 femur, immediately above the external condyle. Below it becomes 

 a large muscle, considerably greater than the inner head of the 

 gastrocnemius, which latter passes down superficially to this second 

 portion. Becoming aponeurotic at the ankle, it contributes to form 

 the superficial plantar fascia, especially that part which underlies 

 the three peroneal metatarsals, its fibres, indeed, appearing to form 

 as it were perforated tendons to the third and fourth digits. 



Plantaris. This muscle is at its origin so intimately connected 

 with the outer head of the gastrocnemius that it is with some hesi- 

 tation that I describe it by a distinct name. About the middle of 

 the leg it separates somewhat from the gastrocnemius externus, and 

 thence widens to the ankle, where it receives a reinforcement of a 

 few muscular fibres from the fifth metatarsal bone, in the distal 

 end of the outer surface of which is implanted a tendon which passes 

 along the peroneal edge of the muscle. In the sole this muscle ap- 

 pears as three fleshy bellies (fig. 18, P.L.A.), which form the per- 

 forated tendons of the second and third digits, and perhaps of the 

 hallux also. 



The popliteus arises from the tibial aspect of the head of the fibula, 

 and is inserted into the posterior surface and tibial margin of almost 

 the upper half of the tibia (figs. 16 & 18, Pp.). 



Flexor lonyus diyitorum (fig. 16, F. P. D., and fig. 18, F. L. !>.). 

 This rather large muscle arises ( I ) partly, in common with the last, 

 irom immediately above the external condyle of the femur, (2) from 

 the upper third of the posterior surface (or margin) of the fibula, 

 and (3) from almost the upper half of the tibial side of the fibula, 



