gS HODGE. [Vol. VII. 



ilar changes in them ? When changes in gland cells were 

 demonstrated for artificial stimulation, the question arose, Why 

 may not similar changes occur in the normal daily activity of 

 the gland .-' So as changes due to artificial stimulation were 

 noted in nerve cells, it was realized that if normal, similar 

 changes should be found in the normal daily rest and activity 

 of the animal. 



While so much space in physiology is given to processes 

 of digestion and nutrition, very little is given to those distinc- 

 tively of rest. Indeed, in a leading physiology of the human 

 body in this country, the subject of sleep is not treated, and 

 even the word "sleep " does not occur, in coarse print, in the 

 book. And yet what fact in physiology is more clearly indi- 

 cated than that of the necessity of rest after activity .■' An 

 animal is awake and active for, we will say, twelve hours. It 

 then sleeps for twelve hours. The sleeping and the waking are 

 dependent, without doubt in chief part, if not entirely, upon 

 processes which are taking place in the cellular portions of the 

 nervous system. To account for such profound functional 

 changes, is it illogical to expect to find correspondingly great 

 changes in structure } The necessity for rest in a gland cell is 

 made apparent by its loss of substance. If nerve cells do not 

 lose substance, or change in some way, why are we tired at 

 night .-* 



III. History of Related Work. 



A knowledge of cellular activity which will enable us to appor- 

 tion to each part of the cell — nucleus, reticulum, granulation, etc. 

 — its peculiar role, to know the purpose for which it exists, and 

 the work which it does for the common good, such knowledge 

 can only be gained by study of physiological activity in cells, 

 and not only in reproductive cells, but in cells of all kinds and 

 functions. It has long been my purpose to sift all the work 

 that has ever been done upon the line of changes in cells due 

 to functional activity, and to glean out whatever consensus of 

 opinion may have been reached. Pressure of other work, and, 

 while in Madison, the lack of all literature, either current or 

 classical, has made it impossible to carry out this plan as fully 

 as desired. A few points require discussion, however, before 

 passing to a consideration of my own experiments. 



