THE MUSCLES 



The study of the muscular system is known as myology. 

 The muscles are of two kinds: voluntary, which are under the 

 control of the will; and involuntary, which cannot be controlled 

 by the will. All muscles moving the bones are voluntary and 

 are supplied with branches of the cerebrospinal nerves. Ex- 

 amples of involuntary muscles are found in the walls of the ali- 

 mentary canal, the ureter, bronchial tubes, and blood-vessels. 

 These are supplied with nerves from the sympathetic nervous 

 system (Fig. ii6). The structure of a voluntary muscle 

 may be seen by teasing a small piece on a slide in a drop of 

 water, covering with a cover-glass, and examining with the 

 compound microscope. It is composed of striated fibers from 

 one to fifteen centimeters in length, while involuntary muscle is 

 composed of cells more or less spindle-shaped and non-striated, 

 except in the heart (Figs. 8 and ii). 



There are over five hundred voluntary muscles in the cat, each 

 of which is usually attached at either end to the periosteum of a 

 bone. The point of attachment on the unmoved bone is 

 known as the origin of the muscle. The insertion of a muscle 

 is its attachment to the bone which it moves. In the case of the 

 biceps, its origin is on the scapula and its insertion on the 

 radius. Usually a muscle originates and terminates in a 

 white glistening cord called a tendon, composed for the most 

 part of white fibrous tissue. 



Each muscle-fiber is surrounded by a transparent elastic 

 sheath, the sarcolemnia. A number of libers bound together 

 by a loose connective tissue, and the whole enveloped by an 

 extension of the same, is a fasciculus. The tissue connecting 

 the fibers is the endomysium, while that enveloping the fasciculus 

 is the perimysium. A number of fasciculi bound together in 

 a sheath, the epimysium, constitutes the entire muscle. The 



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