CHAP. IV MUSCLES 59 



^. ky. genio-hyoid ; gstr. gastrocnemius ; ky.gl. hyoglossus ; ins. ten. tendinous 

 inscription ; /. alb. linea alba ; viy. hy. mylo-hyoid ; obi. int. obliquus internus ; 

 obi. ext. obliquus externus ;■ o. st. omosternum ; p. c. hy. posterior cornu of 

 hyoid \ pet. pectoralis ; pctn. pectineus ; per. peronseus ; ret. abd. rectus ab- 

 dominis ; rect. int. uiaj. rectus internus major ; sar, sartorius ; sb. int. sub- 

 mentalis ; 5i?w. ^^w. semi-tendinosus ; tib. ant. tibialis amicus; //'^.^oj;'. tibialis 

 posticus ; TI. FI. tibio-iibula ; vast. int. vastus internus ; Jtr. st. xiphisternum. 

 (From Parker and Haswell's Zoology.) 



try to find out how the movements are effected in the 

 living frog. 



It was pointed out in the second chapter that the 

 flesh is made up of distinct bands or sheets, the muscles, 

 some of which came under your notice in your first dissec- 

 tion. It is quite easy to convince yourself that the whole of 

 the flesh has this character by skinning a frog and carefully 

 removing the fascia (p. i8) which covers the muscles and 

 the more delicate web of connective tissue which forms a sort 

 of packing substance between them. After noticing some 

 of the muscles shown in Fig. i6, especially those of the leg, 

 concentrate your attention on the muscle marked gstr, a 

 prominent spindle-shaped mass of flesh forming the calf of 

 the leg, and known as the gastrocnemius {gstr). 



The spindle shaped, fleshy mass or belly of this muscle is 

 continued at either end into a band of strong, tough con- 

 nective tissue, the tendon (Fig. 17). The tendon at the 

 proximal end is flat and is attached to the distal end of 

 the femur and to the proximal end of the tibio-fibula, in 

 each case becoming continuous with the periosteum of the 

 bone. The tendon at the distal end has the form of a stout 

 cord and is distinguished as the tendo Achillis ; it corresponds 

 with the strong tendon just above the heel of the human 

 foot. At its distal end it is continued into a broad sheet of 

 connective tissue, the plantar fascia, which spreads over the 

 whole sole or plantar surface of the foot. 



If the foot is bent upon the shank as in the ordinary 

 sitting position of the frog, and the gastrocnemius pulled 



