58 THE MUSCULAR SYSTEM OF THE FROG 



vii. The extensor dorsi communis is a longitudinal 

 mass of muscle arising from the urostyle, and 

 running forwards and slightly outwards : it is 

 inserted into the ilium, into the transverse pro- 

 cesses of the vertebrae, and in front into the 

 posterior end of the skull. The anterior part is 

 divided by transverse tendinous intersections. 



viii. The intertransversales are small muscles, running 

 between the transverse processes of the vertebrae, 

 and lying beneath the extensor communis. 



ix. The glutaeus arises from the outer side of the pos- 

 terior two-thirds of the ilium, and runs backwards 

 to be inserted into the trochanter of the femur. 



B. Muscles of the Head. 

 1. Muscles of the ventral surface of the head. 



i. The mylohyoid or submandibular muscle is a flat 

 sheet of muscle running across from one ramus 

 of the mandible to the other, and divided down 

 the middle line by a tendinous intersection. A 

 narrow strip along the posterior border is 

 commonly separated by a slight interval from the 

 major or anterior part of the muscle. 



Remove the mylohyoid muscle, and the sternal portion of ifte 

 pectoralis. 



ii. The geniohyoid is a narrow longitudinal band a 

 short distance from the middle line : it arises 

 from the lower jaw close to the chin, runs back 

 on the ventral surface of the body of the hyoid, 

 and divides posteriorly into two portions which 

 are inserted respectively into the bony and the 

 cartilaginous posterior processes of the hyoid. 



iii. The sternohyoid is practically the anterior con- 

 tinuation of the rectus abdominis. It arises from 

 the dorsal surface of the coracoid and clavicle, 

 and is inserted into the ventral surface of the 

 body of the hyoid, the tendon passing between 

 the two divisions of the geniohyoid. 



