C 437 ] 



I mention this circumftance to fhew, how cautious we 

 ought to be in drawing conclufions from a folitary fa£lj 

 for had 1 talcen the rhubarb as firfi: propofed, I might have 

 afcribed the unufual pain to this vegetable. 



On the fubfequent night I took it : it excited no pain or 

 inconvenience, and produced an effedl, though lefs than 

 from No. I. I do not hence conclude, that No. II. was 

 weaker, for whatever purgative medicine we give, it is 

 obfervable, that tlie firft dofe afts more powerfully than 

 the fubfequent ones, either from habit diminiQiing the fti- 

 mulus, or from lefs fordes remaining after the firft extiibi- 

 tion of fuch remedies ; as fnufF by ufe lofes its ftimulus 

 on the olfactory nerves. 



It might feem a very natural inference, that a medica] 

 perfon is the beft judge of the effects of medicine, by expe- 

 riments made on himfelf ; but this may be doubtedj as his 

 imagination may be more forcibly direfted to fancy thofe 

 tffefls, which its knowledge induces him to fufpect. We 

 have remarkable proofs in point, in many medical books, 

 whofe authors have related effects of remedies, which none 

 but tliemfelves could difcover. 7'b explain this by a recent 

 inftance: the late celebrated Dr. Storck, who wrote 

 upon the diuretic effects of the Colchicum Autumnale, 

 fancied he could feel its ftimulus on the fecretory organs of 

 urine, and its almoft immediate increafe of that fecrction j 

 which numerous experiments fmce have clearly proved to 

 have depended upon the ardour of imagination. 



This led me to try the rhubarb, where imagination could 

 not operate, I ordered it in about forty ijiftances to cliil- 

 dren from one to three years of age ; I never knew it to 

 produce any griping that was perceptible; it anfwcred as 

 eflectually, or nearly fo, as the beft Turkey, fo far as I could 



Y f 3 afcertain 



