PHYSIOLOGICAL CHANGES IN THE CENTRAL SYSTEM. 283 



however, is the record of the manner in which the nerve 

 impulses followed one another along the spinal cord as 

 the result of stimulating the cerebral cortex, and curve 

 III the record of the stimulus. Since the results occur 

 when the cortical cells alone are stimulated, it is 

 inferred that the peculiar character of the contractions 

 during the epileptic attack depends upon the manner in 

 which the cortical cells discharge. Looking more 

 closely at this reaction, it appears that the discharge 

 begins almost as soon as the stimulus is applied to the 

 cortex, but it may nevertheless go on for some time 

 after it has been withdrawn. The discharge, therefore, 

 takes more time than that occupied by the application 

 of the stimulus ; moreover, it is not continuous, but 

 rhythmical. 



On anatomical grounds the nerve cells are considered 

 separate units, between which not only is there no 

 genetic continuity, but as a rule not even a secondary 

 connection as close as that between the nerve and 

 muscle elements. For this reason it is difficult, strictly 

 speaking, to trace the pathway of a nerve impulse, 

 since now and again there is a gap in its course. As a 

 matter of fact the impulses cross this gap, though the 

 manner of crossing is still unknown. This difficulty has 

 been mentioned in an earlier chapter, and is again 

 stated, since at this point it plays an important part. 

 The cell outgrowths are the channels along which the 

 waves of nerve impulse are guided in their passage 

 through the central system. Repeated incoming impulses 

 produce such changes in the cell-bodies that finally 

 some of them discharge with a force and rhythm of their 

 own, and once taken up by the central cells, even slight 

 stimuli diffuse themselves over the entire central system, 

 although, in any given case, the reactions which we anti- 

 cipate and record may come from only a limited portion 



