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STUDIES IN ADVANCED PHYSIOLOGY. 



ble that these sensory neurons with their capillary dendrons 

 at their ends invest the motor cells which form the first 

 neurons of the motor path. If this be true, it gives to these 

 cells the wonderful faculty of not only serving as voluntary 

 motor cells, but as conscious sensory cells. In other words, 

 in these cortical cells the consciousness of sensation as well 

 '* as the consciousness of volition is located. 



5. Comparison of Sensory and Motor Paths. It will 

 be noticed that in the sensory, as in the motor path, there 

 are essentially two neurons between the periphery and the 

 brain. Further, both sensory and motor neurons cross, either 

 in the medulla, or further down in the cord. An interesting 

 difference between the sensory and motor neurons lies in the 

 fact that in one case the cell body of the lower neuron lies 



Fig. 145. DIAGRAM SHOWING THE PATHS OF FIBERS IN THE CEREBRO-SPINAL SYSTEM. 



Outgoing arrows indicate motor, incoming arrows sensory fibers. 



JK, R, right and left cerebral hemispheres; G, G, gray matter of mid-brain, optic thai- 

 ami and upper medulla; H, H, lower portion of medulla where the cranial nerves take 

 their origin; H,H (at bottom of figure), the gray matter of spinal cord; la, motor nerves; 

 Ib, sensory nerves; 6, G, fibers connecting the hemispheres; Ic, half-crossed optic fibers; 

 5,5, fibers connecting different portions of same hemisphere; 2,2, crossed pyramidal 

 tract; 2', 2', direct pyramidal tract crossing in the cord; #, 3, sensory fibers, some cross- 

 ing in the pyramids (others have crossed in the cord, not shown), but all passing through 

 the gray matter G. By reference to the text the diagram will be more intelligible. 



outside of the spinal cord, in the spinal root ganglion, while 

 in the case of the motor neurons it lies inside of the spinal 



