ANATOMY OF THE BEAVER. 69 



part of the masseter arises further forward by muscle, 

 and still further by tendon, as far as between the 1st 

 and 2d molar, and is inserted into the whole space of 

 the maxillary before the transverse plate, into the an- 

 terior surface of this plate, and its lower arched edge. 

 By means of its anterior tendon, the muscle of one 

 side acting, turns the jaw laterally to the opposite 

 side; while the double action of this part of the mus- 

 cle brings the condyle forward and fixes it in the 

 glenoid cavity for cutting operations. The cutting 

 and grinding power of this muscle must be very great. 

 The temporal muscle arises from the crest on the 

 temporal bone as far back as the occipital crest, and 

 from the parietal bone; also from a tendinous expan- 

 sion extending from the malar to the top of the skull, 

 and from the internal surface of the malar; and is in- 

 serted into the coronoid process of the lower jaw. 

 The pterygoid muscles require no particular descrip- 

 tion. The digastric muscles are large, and fill the 

 space anteriorly between the lateral parts of the jaw. 

 Their tendon in front of the hyoid bone is connected 

 with the mylo-hyoid. Posteriorly they are smaller 

 and are inserted at the base of the mastoid process. 



The tail has free motion laterally; also by exten- 

 sion and flexion, particularly the ktter. An upper 

 lateral muscle connected with the transverse processes 

 of the bones joins the gluteal. Another lateral mus- 

 cle extends from the side of the tail to the tuberosity 

 and ramus of the ischium. The flexors and exten. 

 sors arise from the corresponding surfaces of the sa- 

 crum, and are each in two layers. The flexors are 

 the stronger muscles; they extend to the commence- 

 ment of the scaly portion of the tail, and send great 



