. Animal biology. Zoology; Biology. SUBPHYLUM VERTEBRATA 321 gled with the fibers of the periosteum. In some cases striated muscles have ceased to be under the control of the will and thus in a sense have become involuntary. Such are some of the muscles used in swallow- ing. The involuntary, or non-striated, muscles are found mostly in the walls of the alimentary canal and the blood vessels. The cardiac muscles are in the wall of the heart. Both involuntary and cardiac muscles are usually not recognized as part of the muscular system but as parts of the systems to which the organs containing t
. Animal biology. Zoology; Biology. SUBPHYLUM VERTEBRATA 321 gled with the fibers of the periosteum. In some cases striated muscles have ceased to be under the control of the will and thus in a sense have become involuntary. Such are some of the muscles used in swallow- ing. The involuntary, or non-striated, muscles are found mostly in the walls of the alimentary canal and the blood vessels. The cardiac muscles are in the wall of the heart. Both involuntary and cardiac muscles are usually not recognized as part of the muscular system but as parts of the systems to which the organs containing them belong. 346. Digestive System.—The digestive systems of different verte- brates present many modifications. In general the system may be Scopulo Acetabulum Femur. Coracoid ] Clavicle Radius AyW//?fP Me fa tarsals I ^ 17 py'Phalanges ^ocac^C^ Fibula —<^ Phalanges Fig. 214.— Diagram to illustrate the homology between the skeletons of the fore and hind limbs. divided into an alimentary canal, beginning at the mouth and ending at the anus, and accessory organs, including glands connected to the ali- mentary canal by ducts. The regions of the alimentary canal are, in order, mouth, pharynx, esophagus, stomach, and small and large intes- tines (Fig. 215). The mouth cavity, also called the buccal cavity, usually contains jaws bearing teeth for the mastication of the food and a tongue which is used in handling the food and may assist in securing it. In connection with the mouth may be several pairs of salivary glands the secretion of which, the saliva, contains an enzyme, ptyalin. This in an alkaline medium con- verts starches into sugars. The saliva also contains the secretion of mucous glands lying in the walls of the mouth; it serves to moisten the food and make its swallowing Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfec
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