_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 longitudinal 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 covering 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 continuation of a muscle, it is called an aponeurosis. =The Muscular Nomenclature.=—In the fowl there are 162 muscles, single or in pairs. These muscles are named from their location, as the lingualis; others from their attachments, as the dermo-temporalis; 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 quills 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 origin and insertion to the under surface 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 =Dermo-frontalis.=[3] _Location._—This muscle is somewhat rudimentary and may be entirely absent. It is located in the frontal region and is about 2 or 3 centimeters long and not so wide. Footnote 3: The classification of Shufeldt is used. _Origin and Insertion._—Closely attached to the skin. _Shape._—Flat and rather rectangular. _Relations._—Superiorly with the skin and inferiorly with the frontal bones. _Action._—By contraction the feathers on the top of the head lie flat. Those above the eyes are elevated. =Dermo-dorsalis.= _Location._—In the median line of the neck and back.