The Muscular Tissue
The muscle are formed of bundles of reddish fibers, endowed with the property of contractility. The two principal kinds of muscular tissue in the body are voluntary and involuntary. The former of these, from the characteristic appearances which their fibers exhibit under the microscope, are knows as the "stripped" muscles, and from the fact that it is capable of being put into action and controlled by the will, as "voluntary" muscle. The fibers of the latter do not present any cross-stripped appearance, and for the most part are and under the control of the will; hence they are known as the "unstripped" or "involuntary" muscles. The muscular fibres of the heart differ in certain particulates froin both these groups, and they are therefore separately described as "cardiae" muscular fibers.Thus it will be seen that there are three varieties of muscular fibres:
- Thransversely striated muscular fiber which are for the most part voluntary and not so, such as the muscles of the pharynx and upper part of the aesophagus. Thin variety of muscle is sometime called skeletal.
- Transversaly striated muscular fibers, which are not under the control of the will, i.e, the cardiac.
- Plain or unstripped muscular fibers, which are involuntary and controlled by a different part of the nervous system from that which controls the activity of the voluntary muscle. Such are the muscular walls of the stomach and intestine, of the uterus and bladder, of the blood vessels, etc.
