130 



COUES, 



thicker and narrower as it passes forward to definite insertion (fleshy, 

 or by a very short tendon) into the pectoral crest of the humerus, 

 alongside the insertion of the pectoralis major. The anterior border 

 of this dermo-brachialis corresponds in a general way with the poste- 

 rior border of the great pectoral. A third distinct slip, large and im- 

 portant, forms what may be called the costo-dermal fasciculus. It 

 arises by two definite fleshy digitations from the 12th-13th ribs, respec- 

 tively 1' and lh' from the back-bone, and forms a long, slender, fiat rib- 

 bon, that runs straight up the side of the body along the anterior 

 border of the lower trapezius, underneath the main plane of the pan- 

 niculus, lying upon the latissimus, to the shoulder; passing just behind 

 the elbow, widening over the 'shoulder, becoming then blended with 

 the panniculus along the side of the neck, then separating again, and 

 finally inserted into the back part of the cheek-pouch. 



In considering the form and uses of this great muscle, probably 

 representing the extreme case of its development in the mammalian 

 series, we are struck first with its nearly equal and essentially sym- 

 metrical presence on both the anterior and posterior halves of the 

 body. Acting as a whole we see how, in connection with the thick 

 skin, dense fur, and subjacent flocculent areolar tissue, it contributes 

 to fill up the various irregularities of the surface of the body, and pro- 

 duce a shape offering least resistance in passing through the water ; 

 while, moreover, this everywhere contractile tunic must largely assist 

 in producing the various undulatory motions of a body suspended in a 

 fluid of nearly its own specific gravity. Its two lateral caudal prolon- 

 gations resemble tiller-ropes to guide the side motions of the rudder- 

 like tail; its two lateral costal slips bend the whole body sideways. 

 The hyoid slip is a retroductor of that bone, in action intermediate 

 between sterno- and omo-hyoid. The brachial fasciculus acts like 

 an accessory pectoralis major. The cheek-pouch slip pulls that organ 

 directly backward, and appears to be in antagonism with the special 

 orbicular muscle that surrounds and contracts the pouch ; while the 

 transverse fibres that spread over the latter compress it and assist 

 the orbicular muscle in emptying it. (The dissection was here a little 

 obscure, owing to laceration of the parts ; but we believe such is 

 the arrangement.) Finally, the fascial attachment of the muscle at the 

 lower arm and leg, where the limbs protrude through the orifices, 

 renders the panniculus an accessory mover of the limbs in various 

 directions. 



II. Vertebral Muscles. 



a. Of the Head. 



Unfortunately, the shattered state of the parts prevented any satis- 

 factory dissection here. 



b. Of the Neck. 

 (a'. — Anterior vertebral.) 



