

PHYSIOLOGY. 53 



rcneous, in so far as our judgment depends upon a number of 

 different circumstances in our own organs, each of which may 

 be changed without our being aware of it, or perceiving it, 

 and therefore we judge differently. The opticians will afford 

 us many instances of this, with regard to the magnitude, dis- 

 tance, figure, and even number of objects. I need not insist 

 upon the particulars, as they will readily occur to you in con- 

 sidering the subject These are errors of sense, which de- 

 pend upon changes in the state of the external object itself, 

 and, therefore, we are not concerned with them ; only when 

 they are from a change in the state of our organs, they are 

 to be studied in Pathology, 



" 3, We conceive it as an error of sense when we perceive 

 the qualities of bodies in a very unusual manner, or when 

 these qualities have a very unusual effect upon us. I say the 

 qualities of bodies affect us in a very unusual manner, when 

 our judgment of these qualities is totally changed ; as when we 

 perceive asafoetida to be an agreeable odour, and musk to be 

 remarkably disagreeable ; instances of both these are common, 

 and are certainly contrary to the most general state of sensation 

 among mankind ; or when the small portion of the white of an 

 egg, which is a bland mild substance, taken into a certain 

 stomach produces violent pain and other disorders; this is 

 more uncommon. Many of the singularities mentioned by 

 physicians under the title of Idiosyncrasies, are of the same 

 kind ; they are to be considered as errors of sense, and have been 

 called depravities of sense. Dr. Whytt mentions these depravi- 

 ties of sense as one of the principal causes of nervous diseases, 

 ( Works, p. 543.) Some very curious questions may be started; 

 e. g. in the case of Idiosyncrasies of the stomach. It may be 

 a question whether the effect depends upon the action of the 

 substance that is thrown in, acting upon a peculiar condition of 

 the nerves there, or if it depends upon the substance thrown in 

 occasioning a peculiar fermentation there, or modifying, in a pe- 

 culiar manner, the usual fermentation of the stomach, and 

 thereby producing a matter in it which would act upon every 

 other stomach. Thus, with regard to the effects of honey when 

 taken into some stomachs, a strong suspicion arises that they de- 



