66 



TEXT-BOOK OF PHYSIOLOGY. 



MUSCLE 

 FIBER 



CAPILLARY BLOOD 

 VESSEL 



eating that the former is doubly refracting or anisotropic, the latter 

 singly refracting or isotropic. 



The Blood-supply. Muscles in the physiologic condition re- 

 quire for the maintenance of their activity a large amount of nutritive 

 material. This is obtained from the blood furnished by the blood- 

 vessels. The vascular supply to the muscles is very great and the 

 disposition of the capillary vessels with reference to the muscle - 

 fiber is very characteristic. The arterial vessels, after entering the 

 muscle, are supported by the peri-mysium; in this situation they give 

 off short, transverse branches, which immediately break up into a 

 capillary network of rectangular shape within which the muscle- 

 fibers are contained. The muscle-fiber, in intimate relation with 

 the capillary, is ^th prl _with lymph derived from it. Its contractile 



substance, however, is separ- 



LYMPH SPACE ated from the lymph by its 



own investing membrane, 

 through which all interchange 

 of nutritive and waste mate- 

 rials must take place. The 

 relation of the capillary vessel 

 to the muscle-fiber is shown 

 in Fig. 1 8. 



The .nutritive material 

 passes through the capillary 

 wall into the lymph- space, 

 then through the sarcolemma 

 into the interior of the fiber, 

 where it comes into relation 

 with the living muscle mate- 

 rial. AThe waste products aris- 

 ing in the muscle as a result 

 of nutritive changes pass in 

 the reverse direction into the 

 blood, by which they are car- 

 ried away to eliminating or-/ 



gans. Lymphatics are present in muscle, but confined to the COIP 

 nective tissue, in the spaces of which they take their origin. 



The Nerve-supply. The nerves which carry the stimuli to a 

 muscle enter near its geometric center. Many of the fibers pass 

 directly to the muscle-fibers with which they are connected; others 

 are distributed to blood-vessels. Every muscle-fiber is supplied 

 with a special nerve-fiber except in those instances where the nerve- 

 trunks entering a muscle do not contain as many fibers as the muscle. 

 In such cases the nerve-fibers divide near their termination until the 

 number of branches equals the number of muscle-fibers. The 



FIG. 1 8. RELATION OF THE BLOOD-VESSEL 

 TO THE MUSCLE-FIBER. 



