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THE POPULAR SCIENCE MONTHLY. 



ing or " centripetal " fiber which shall proceed to another collection of 

 cell-matter. In the cerebro-spinal system we have the lowest nerve- 

 arc brought into close anatomical relation with the large cell-mass of 

 the cerebral hemispheres, as well as with the lower cell-masses, by 

 ascending and descending fibers. 



I am now to indicate the functions of the parts of this system pre- 

 viously described, and first the spinal cord. This organ has two dis- 

 tinct functions — these are transmission of motions and independent 

 nerve activity. As conductor of motions the cord is related to the 

 higher encephalic centers. By transmission of motions from the sur- 

 face of the body along an afferent fiber to the cell-mass of this cord, 

 and thence to the brain, sensations are made possible. By transmission 

 of motions fi'om the brain along efferent fibers down the antero-lateral 

 columns of the cord to the anterior roots, and thence to muscles sup- 

 plied by these roots, voluntary movements are made possible. This 

 teaching should be emphasized. We are dependent on the anatomical 



FtG. 6.— ITndkr Surface op the Human Brain. (Allen Thomson.) 1,1, great longitudinal fis- 

 sure ; 2, 2', 2", convolntions of under surface of frontal lobo ; 3, 3, 3, prolongation to base of the 

 fissure of Sylvius ; 4, 4', 4", convolutions of the temporal lobe ; 5, y, occipital lobe; 6, anterior 

 pyramids of medulla ; + , posterior extremity of median lobe of cerebellum ; 7, 8, 9, 10, lobules 

 of the lateral lobe of the cerebellum. I-IX. Cranial nerves, all but the first more fnlly seen in 

 the next figure. The ninth nerve of the right side has been removed. X. First cervical nerve. 



integrity of the spinal cord and encephalic centers for any direct sensa-" 

 tion, knowledge of things affecting nine tenths of our body, and also 

 for any exercise of volition upon these parts of our body. Conscious- 

 ness and volition, as far as they relate to any direct connection between 

 ourselves and a large part of our physical organism, are entirely con- 



