416 MAURY OX SLEEP AND DREAMS. 



the same organisation which ministers to the sen- 

 sorial functions of the day. Through the microscope 

 and other means much has been discovered of the 

 minute anatomy of the brain and its appendages. 

 Medullary cells and fibres, ganglionic centres, and new 

 nervous intercommunications have been disclosed ; and 

 though less assuredly, certain functions localised as 

 regards the parts of the brain fulfilling them. But of 

 the infinitesimal motions and changes in the nervous 

 substance itself, we are as entirely ignorant as we are 

 of that mystery which associates these changes in 

 invisible mechanisms with the intellectual and spiritual 

 part of our nature with the sensations, thoughts, 

 memories, and emotions, which in their succession and 

 combinations constitute the mental being of man. We 

 must not indeed vaunt our knowledge of the brain 

 until all dispute is settled as to the functions of the 

 Cerebellum one of the most prominent parts of the 

 cerebral system, and unquestionably fulfilling functions 

 essential to the integrity of the whole. 



What, however, we are mainly concerned with here 

 is the fact that actions analogous in kind, though 

 variously altered in operation, occur alike in the sleep- 

 ing and waking brain. In reasoning upon the physical 

 causes of these phenomena, we do not reach our end 

 in merely proving the influence of changes in the 

 cerebral circulation and of varying pressure thus pro- 

 duced. We advance a step, but only one step, by this 

 demonstration; leaving it unsettled whether the ex- 

 haustion of nerve force, the primary cause of sleep, is 

 not also the immediate cause of these very changes in 



