VESANIJE. 515 



cal, of the nervous power or fluid in these different states. 

 (Compare Physiology, CXXXL)" 



MDXLV. That these different states of excitement and col- 

 lapse take place on different occasions, must, I think, be mani- 

 fest from numberless phenomena of the animal economy : but 

 it is especially to our present purpose to observe, that the dif- 

 ferent states of excitement and collapse are in no instance more 

 remarkable, than in the different states of waking and sleeping. 

 In the latter, when quite complete, the motion and mobility of 

 the nervous power, with respect to the whole of what are called 

 the Animal Functions, entirely cease, or, as I would express it, 

 are in a state of collapse : and are very different from the state 

 of waking, which in healthy persons I would call a state of gen- 

 eral and entire excitement. 



MDXLVI. This difference in the states of the nervous 

 power in sleeping and waking being admitted, I must in the 

 next place observe, that when these states are changed from the 

 one into the other, as commonly happens every day, the change 

 is hardly ever made instantaneously, but almost always by de- 

 grees, and in some length of time only : and this may be ob- 

 served with respect to both sense and motion. Thus, when a 

 person is falling asleep, the sensibility is gradually diminished : 

 so that, although some degree of sleep has come on, slight im- 

 pressions will excite sensation, and bring back excitement ; 

 which the same, or even stronger impressions, will be insufficient 

 to produce when the state of sleep has continued longer, and is, 

 as we may say, more complete. In like manner, the power of 

 voluntary motion is gradually diminished. In some members 

 it fails sooner than in others ; and it is some time before it be- 

 comes general and considerable over the whole. 



The same gradual progress may be remarked in a person's 

 coming out of sleep. The ears in this case are often awake be- 

 fore the eyes are opened or see clearly, and the senses are often 

 awake before the power of voluntary motion is recovered ; and 

 it is curious to observe, that in some cases, sensations may be 

 excited without producing the ordinary association of ideas. 

 (See Mem. de Berlin, 1752.) 



MDXLVII. From all this, I think it will clearly appear, 

 that not only the different states of excitement and collapse can 



2x2 



