THE CENTRAL NERVE SYSTEM 351 



and dendrites of the ganglia on its root, to the groups 

 of cells in the dorsal horn of the spinal cord, and as 

 we have mentioned before, these impulses ascend and 

 descend by means of collateral branches, axones, and 

 dendrites, communicating with other centres in the 

 cord at different levels and ultimately reach the 

 sensor areas in the brain. The anterior root is motor 

 or efferent, and contains axones which transmit 

 impulses from the groups of cells or centres in the 

 anterior horn of the spinal cord, which are further 

 conveyed by means of the efferent axones or nerve 

 fibers to the periphery, where they stimulate muscles, 

 glands, viscera, etc., into activity. 



In other words, motor impulses arise in the cells of 

 the anterior horn of the spinal cord and the motor area 

 in the brain, and are conveyed toward the periphery 

 of the body (muscles, glands, etc.), by means of 

 neurones and their efferent processes. Sensor impulses 

 arise within the structures of the skin, mucous mem- 

 brane, etc., and are conveyed to the sensor group of 

 cells in the dorsal horn of the cord, and are trans- 

 mitted to the sensor and conscious areas in the 

 brain by aggregations of neurones and their (afferent) 

 processes coursing through the cord and brain sub- 

 stance. 



The functions of the spinal cord are classified under 

 anatomatism, reflex action, association conduction, sensor 

 conduction, motor conduction. 



Automatism, or Automatic, Autochthonic Action. 

 This is a function possessed by the spinal nerve cells 

 whereby they influence the growth, development, and 

 nutrition of the numerous cells of the various tissues, 

 and thus maintain their normal physiologic activity. 

 By this expression is meant a discharge of energy 

 from the cells occasioned by a change in their environ- 

 ment, i. e.j in the chemic composition of the blood or 

 lymph by which they are surrounded, and independent 



