50 PHYSIOLOGY. 



'& 



certainly, innumerable operations of this kind going on in the bo- 

 dy. Though certain substances stimulate the kidneys we are not 

 sensible of it ; and so with regard to the stomach ; if we take a 

 dose of ipecacuan, it has operated for some time upon the stomach 

 before we have any sensation of nausea ; this only follows an 

 operation of which we are not conscious ; and I imagine that it 

 is an established law of our system, that certain states of our 

 stomach operate upon distant parts of the body without our be- 

 ing conscious of the operation, or of the effects. Thus we 

 have a fact from Van Swieten, of a person who, by taking a 

 small quantity of crab's eyes, had an efflorescence upon the 

 surface of the body, which disappeared upon the crab's 

 eyes being thrown out of the stomach. Now, here is a com- 

 munication that cannot be said to be attended with any degree 

 of sensation ; and there may be many more of the same kind.' 



" I now proceed to consider the errors or depravities of sense 

 which we cannot refer to the different degrees of sensibility. 

 With regard to this subject, I think it maybe supposed to con- 

 sist in these three particulars 1. Our perception of things 

 that do not exist, or our supposing matters to exist that have 

 no real existence. 2. In our judgment of things really exist- 

 ing without us, our perceiving them otherwise than they really 

 exist. 3. When the qualities of impression do not operate in 

 the usual manner. But of each of these more particularly. 



"1. The first of these is what we more strictly call imagina- 

 tion ; and, with regard to it, I have said in LXIX. that it 

 seems to depend upon internal causes, i. e. upon causes acting 

 in the brain. If I had qualified this with the word chiefly, I 

 should have been correct ; but as it stands it is not just, for 

 there are imaginations that are false, which depend upon 

 impressions made not only upon the brain, but upon other 

 parts of the nervous system, and even upon the sentient 

 extremities. I was once informed, by a gentleman of great ve- 

 racity, of a singular occurrence to this purpose. A lady was 

 attacked with a disorder of the hysteric kind ; and she imagined 

 she was surrounded with goblins and spectres, which followed 

 her from one part of the room to another. Her physician and 

 surgeon were present in one of these fits, and they endeavoured 



