THE MUSCULAR SYSTEM 41 



Great care should be exercised to avoid removing the 

 cutaneous muscles, which are located immediately under 

 the skin. The student should be provided with two rats, 

 one for the study of the muscles, the second for the dis- 

 section of the remaining soft parts. Only the larger super- 

 ficial muscles are included in the following account. 



MUSCLES OF THE SKIN 



The cutaneous maximus muscle spreads out fanwise from 

 the region of the arm pit. It covers the back from the 

 shoulders to tail, the sides of the trunk posterior to the 

 front leg, and a large part of the ventral surface of the 

 trunk. Its function is to move the skin, in which it is 

 inserted. 



The platysma is a thin sheet of muscle which radiates 

 from the posterior angle of the mouth, covers the posterior 

 side of the face and the lateral surface of the neck, and 

 sends a branch up in front of the ear. The broad cervical 

 portion is attached along the middorsal line of the neck. 



Exercise X. Sketch the cutaneous maximus and platysma mus- 

 cles into an outline drawing of the lateral view of the rat. 



Carefully remove the two preceding muscles. 



SUPERFICIAL MUSCLES OF THE HEAD 

 (LATERAL VIEW) 



Masseter. This muscle consists of two main parts, an 

 external and an internal. Anteriorly these two are dis- 

 tinct, but they blend posteriorly. 



Internal part. Origin, the whole^ length of the zygomatic 

 arch. Insertion, the mandible, posterior to the diastema. 

 Anteriorly the fibers run nearly at right angles to the 

 long axis of the jaw ; posteriorly they form an acute angle 

 with this axis. 



