NIGHTMARE. 559 



their object may be quite trivial, and in its attainment considerable risks 

 may be run. In these cases it seems as if the mind was absolutely wrap- 

 ped up in one idea, and wholly unable to comprehend any thing else. If 

 the eyes of the somnambulist are wide open, he sees nothing, and even 

 though a bright light be presented before him, the iris will not contract, 

 yet he moves about in a manner as if he were, in one respect, guided by 

 understanding, the air of his movements being as if he knew what he 

 was about, yet in another respect as though he was impelled by the 

 most unaccountable folly, walking along the roof of the house, seating 

 himself on the chimney, and finding his way in safety over precipitous 

 places, past which it would be impossible he should go if awake, no mat- 

 ter how steady his head might be. Besides this complete condition of 

 somnambulism there are intermediate forms, during which the various 

 senses of seeing, hearing, etc., are in partial activity. There are also 

 differences in the intensity or depth of the state, as is shown by the ease 

 or difficulty with which the individual is aroused ; sometimes to speak 

 to him is enough, sometimes he must be violently shaken or otherwise 

 roughly treated. It has been observed in some cases that where the pa- 

 tient spontaneously wakens under circumstances that affright him, he is 

 at once broken of the habit. 



With dreams and somnambulism is also to be classed that sensation 

 which often surprises and disturbs us when we are just passing Sensation 

 into sleep, a sensation as though we were suddenly falling down of fallin s- 

 stairs. This, with some persons, is of almost nightly occurrence. Its 

 opposite, an inability to move, as though we were oppressed by some 

 great weight, or spell-bound in some incomprehensible way, is nightmare. 

 In this distressing affection there is a sense of oppression at Nightmare : 

 the epigastrium, and a difficulty, or rather impossibility, of its causes - 

 moving or speaking. A frightful dream, in which some alarming object 

 is depicted with intolerable distinctness, accompanies these symptoms, 

 the attack terminating by a struggle to shake off the object of dread, or 

 to escape by flight, or to speak. On awaking, the sufferer finds himself 

 trembling with terror, the respiration hurried, and the heart throbbing 

 violently. The intellectual faculties are on different occasions in vari- 

 ous states of activity, and sometimes the dream, and our actions conse- 

 quent upon it, offer no violation of reason. Indeed, some individuals are 

 affected by this trouble during the daytime, when they are wide awake 

 and perfectly aware of what is going on ; but, whether it occurs by night 

 or by day, the sentiment with which it oppresses is that of unspeakable 

 dread. Even at night we sometimes are conscious of its approach, when 

 we are in the intermediate state between sleeping and waking. 



The cause of nightmare, in all its variety of forms, is disturbance of 

 the respiratory function, which, by interfering with the arterialization of 



