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TEXT-BOOK OF PHYSIOLOGY. 



c. s.c. 



DC.. 



SC 



FIG. 12. DIAGRAM SHOWING THE RELATON OF SKELETAL, MUSCLE AND NERVE 

 TISSUES. (G. Bachman.} /.a. Bones of the forearm representing the skeletal tissue; e.j. 

 the elbow joint, the fulcrum of the lever formed by the bones of the forearm; W. a weight 

 acting in a downward direction and representing the passive force of gravity; sk.m. a 

 skeletal muscle acting in an upward direction and the source of the active power to be ap- 

 plied to the lever; sp.c. transection of the spinal cord showing the relation of the white and 

 the gray matter: m.c. a motor cell in the anterior horn of the gray matter; ef.n. an effer- 

 ent nerve-fiber connecting the motor cell from which it arises with the skeletal muscle and 

 contained in the ventral roots of the spinal nerves; a/.n. an afferent nerve-fiber arising from 

 the ganglion cell along its course and connecting the skin, s., on the one hand with the spinal 

 ford on the other hand and contained in the dorsal roots of the spinal nerves; c.s.c. 

 coronal section of the cerebrum showing the relation of the gray to the white matter; v.c. 

 a volitional or motor cell; d.a. a descending axon or nerve-fiber connecting the volitional 

 cell from which it arises with the motor cell in the spinal cord; s.c. a sensor cell; a.a. an 

 ascending axon or nerve-fiber connecting a receptive cell from which it arises (not shown in 

 the diagram) with the sensor cell in the gray matter of the cerebrum. The nerve-fibers 

 which pass outward from the spinal cord to the glands, blood-vessels, and the muscle 

 walls of the viscera, have for the sake of simplicity been omitted from the diagram. 



