271 



9. M. peronceus longus (y), 0*03 oz. 



Origin ; from the shaft of the fibula, and from the tendon of the 



biceps femoris (d). 

 Insertion ; into the outer tarsal bone, uniting with the tendon of 



the gastrocnemius. 



1 0. MM. tibialis anticus et extensor digitorum communis (z), . 0*11 oz. 



Insertion; into the tarsal end of the 1st, 2nd, and 3rd metatarsal 

 bones. 



The interlacing of muscles in the thigh and leg of the Crocodile, 

 just described, is very remarkable, and more complicated than that 

 found even in the Ostrich; and at first I was disposed to think that it 

 threw some doubt on the explanation I had given previously of the 

 reason for such an arrangement in the bird's leg. In the case of the 

 Ostrich the necessity for strict simultaneity of action was made evident 

 by the great force of the muscles employed, and the great delicacy of 

 the bones on which they had to act. Y/hat could there be in the case 

 of the Crocodile to correspond to such a peculiarity in the case of the 

 Ostrich ? After some careful dissection I found the ready answer to my 

 question in the remarkable muscle which I shall now describe. 



On clearing away the superficial muscles of the thigh and tail, I 

 found the enormous mass of muscle, figured at b, Fig. (20), which acts 

 as the chief and powerful extensor of the thigh. 



11. M. extensor femoris caudalis {b)* 1-81 oz. 



Origin ; from the transverse and inferior spinous processes of the 

 caudal vertebras, from the 3rd to the 15th, inclusive. 



Insertion ; into the back of the upper part of the femur, and into a 

 great round tendon, which receives, in particular, the anterior 

 fibres of this enormous muscle, and, passing down the back of the 

 femur, is inserted by a strong common aponeurosis into the outer 

 condyle of the femur, and into the head of the fibula. This com- 

 mon aponeurosis also gives a partial origin to the gastrocnemius 

 (a), Pig. 20, and to the plantaris (x), Tig. 19. 



* This remarkable muscle is noticed and accurately described by Meckel, in tome iii., 

 pp. 152, 153, of his "System der vergleichenden Anatomie" (Halle, 1828); but it is very 

 strange that he transposes its origin and insertion, and seems not to have had any idea of 

 its real use. It is regarded from his point of view as a descriptive anatomist, and without 

 the remotest reference to its final cause. He says : — " Der zweite, tiefere weit dickere 

 Muskkel is von dem ersten [the superficial muscle of the tail] wie einer breiten Binde 

 umgeben, entspringt mit zwei ganz getrennten, 1) einer weit kiirzern, breiten .Sehne oben 

 von den hintern Flache des Oberschenkelbeines ; 2) durch eine weit langere, schlanke, 

 unten zwischen den beiden Gelenkknorren desselben Knockens, und setzt sich an die 

 ganze Seitenflache der untern Dornen, so wie der Zwischendornenhaut. und die untere 

 Flache derWurzeln der Querfortsatze." 



