CHAP, iv MUSCLES 59 



gn. hy. genio-hyoid ; gstr. gastrocnemius ; hy. gl. hyoglossus ; ins. ten. tendinous 

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

 obi. ext. obliquus externus ; o.st. omosternum ; p. c. hy. posterior horn of hyoid 

 pet. pectoralis ; pctn. pectineus ; per. peronaeus ; ret . abd. rectus abdominis 

 reel. int. rnaj. rectus internus major ; rect. int. min. rectus internus minor 

 sar. sartorius ; sb. nit. submentalis ; sent. ten. semitendinosus ; tib. ant. tibialis 

 anticus ; tib. post, tibialis posticus ; TI. FI. tibio-fibula ; vast. int. vastus 

 internus ; x. st. xiphisternum. (From Parker and Haswell's Zoology.) 



We must now 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 

 dissection. 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. 18) which 

 covers the muscles and the more delicate web of con- 

 nective-tissue which forms a sort of packing substance 

 between them. After noticing some of the muscles 

 shown in Fig. 16, especially those of the leg, give your 

 attention to 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 

 connective-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 A chillis ; 

 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 



