MYOLOGY. 



GENERAL MYOLOGY. 



Myology is the study of the muscles and of their accessory structures, such as tendons, 

 aponeuroses, fascia?, intermuscular septa, tendinous arches, pulleys, mucous bursa?, tendon- 

 sheaths (vagina mucosa), tendon retinacula, and sesamoid bones. 



The musculature of the human body occurs in two forms which present both histological and 

 physiological differences (see "Atlas and Epitome of Normal Histology," Sobotta-Huber). The 

 actual skeletal muscles are composed only of striated muscular tissue. 



The muscles form the fleshy portion of the body, and are contractile structures which van- 

 considerably in size and shape. A typical muscle is composed of a muscular belly, which forms 

 the greater portion of it, and of two ends, one of which is known as the origin, or head, and the 

 other as the insertion, the origin being that end which is attached to the usually more fixed portion 

 of the skeleton and the insertion that attached to the more freely movable portion, but the physio- 

 logical relation of origin and insertion may be reversed. As a rule, both the origin and the 

 insertion possess a tendon of varying length, winch is usually considerablv thinner than the 

 muscle. 



Muscles are distinguished according to their shapes. A great many, particularlv those 

 forming the mass of the extremities, are fusiform or spindle-shaped, while others are broad, thin, 

 and flat; muscles whose length but slightly exceeds their breadth are designated short mu'scles! 

 Some muscles surround orifices of the body or canals, and their fibers are circularly arranged; 

 they are known as orbicular muscles, or, if they serve to close orifices, such as the mouth, for 

 example, as sphincters. Those muscles in which the fasciculi pass to a tendon developed at' the 

 side of the muscle arc known as pinnate or penniform muscles, and if the tendon be situated in 

 the middle and receives muscular fasciculi from either side, the muscle is said to be bipinnate 

 or bipenniform. 



The majority of the muscles have a single head, but occasionally two, three, or four heads 

 unite to form a muscular belly, producing a biceps, triceps, or quadriceps muscle. A muscle com- 

 posed of two bellies with an intervening tendon is termed a biventer or digastric muscle. 



If muscles pass only over one joint of the body (particularlv in the extremities), they are 

 known as monarticular muscles; if they extend over two main joints in their course, they are 

 called biarticular. 



Tendons occur in connection with nearly all the muscles, and are completely absent in the 

 sphincters only, though par.lv wanting in the orbicular muscles. Every muscle, however, has 

 not a tendon at both ends, it frequently happening that only the tendon of insertion is developed, 

 while the origin is purely muscular. The fibers of the tendons of origin or insertion are very 



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