530 PHYSIOLOGY, 



fasciculi contained within it; thus, the glutei are coarse, the muscles 

 of the eye fine. 



The length of the fasciculi is not always the same as the length 

 of the muscle; this characteristic depends upon the arrangement of 

 the tendons to which the muscle is attached. When the tendons are 

 attached to the ends of a long muscle, as the sartorius, the fasciculi 

 run from one end of the muscle to the other and so are of consid- 

 erable length. However, a long muscle may be made up of a series 

 of short fasciculi attached obliquely to one another by beveled ends. 

 Short fasciculi thus attached, as in the rectus muscle of the thigh, 

 have stronger action than where they run the extent of the muscle. 



FIBERS. The form of the muscle-fibers is cylindrical or prism- 

 atic with rounded angles. Their diameter varies very considerably, 

 even in each muscle, although a certain standard is found to exist in 

 every muscle. The largest human fibers average one-tenth of an inch 

 in diameter, and fiom that size to one two-hundred-and-fiftieth of an 

 inch fibers may be found. Between the size of the muscle and that 

 of its fibers there is no constant relation. 



The length of the muscular fibers does not generally exceed one 

 and one-half inches. Thus, in a long fasciculus, the fibers do not 

 reach its whole length, but end in a rounded or tapering end invested 

 with sarcolemma and cohering with neighboring fibers. There is, as 

 a rule, no anastomosis or division of the fibers of a muscle, except in 

 the tongue of a frog, where they branch beneath the mucous mem- 

 brane to which they are attached. The same thing has been observed 

 in the tongue of man. 



SARCOLEMMA. The sarcolemma is a tubular sheath inclosing the 

 soft substance of the muscle. It is an elastic, transparent, homoge- 

 neous membrane; it is rather tough and can remain intact even 

 though the muscle be ruptured. Upon its inner side are found nuclei 

 which, however, belong to the muscle rather than to the inclosing 

 membrane. 



Structure. With a low magnifying power, the muscle presents 

 clear pellucid fibers which are cross-striped with bands alternately 

 dark and light. That this striation is not on the surface alone, but 

 extends throughout the substance of the muscle, is readily demon- 

 strated by altering the focus of the microscope. The stripes do not 

 occur on the sarcolemma, but throughout the sarcous substance in- 

 closed by the former. 



The breadth of the bands is about 1 / 17000 inch, so that eight or 

 nine dark bands may be counted in 1 / 1000 inch. While this is the 



