MYOLOGY 71 



are arranged in sheets and aid in forming the walls of the digestive 

 tract, to which they give the power of contraction and expansion. 



Involuntary-striated, or heart muscle (Fig. 77, No. 4), occupies 

 an intermediate position between the two muscles just described. 

 It is composed of cells which branch, are somewhat rectangular. 

 They possess both longitudmal and transverse striation. Among 

 the fibers is found a small amount of connective tissue, as in the 

 former types of muscle, which gives support to the blood-vessels 

 and nerves. 



Fascia. — The term fascia is applied to membranous expansions, 

 differing materially in strength, texture, and relations. Fascia is 

 composed of loosely arranged white fibrous connective tissue. At 

 least two layers may usually be distinguished, the superficial fascia 

 and the deep fascia. 



Below the skin is the superficial fascia, which forms a continuous 

 covermg over the whole body and serves to attach the skin to the 

 underlying structure. 



The deep fascia more densely constructed, may be attached to 

 the skeleton, ligaments, and tendons. 



When the fascia spreads out, becomes denser, and acts as a con- 

 tinuation of a mucle, it is called an aponeurosis. 



The Muscular Komenclature. — In the fowl there are 162 muscles, 

 single or in pairs. These muscles are named from their location, 

 as the Ungualis; others from their attachments, as the dermo-tem- 

 poralis; some from their form, as the rhomboideus; others from their 

 use, as the flexor or extensor; and still others from their direction, 

 as the transversus. 



THE Dermal muscles 



Birds are provided with a system of delicate muscles divided into 

 numerous fasciculi, which harmoniously act upon the feather quiUs 

 and collectively agitate the plumage. These are the dermal muscles. 

 This group is divided into two subgroups : the true dermal muscles, 

 that is, those that have their origm and msertion to the under sur- 

 face of the skin; and the dermo-osseous, those that originate on the 

 surface of some bone and insert to the inner surface of the skin. 



TRUE DERMAL MUSCLES 



Dermo-frontalis Dermo-dorsalis 



Dermo-tensor patagii Dermo-humeralis 



Dermo-pectoralis 



