08 LETTERS TO BROTHER JOHN. 



these will either not affect it at all;, or affect it 

 painfully and injuriously. Thus sound, being a 

 stimulus proper to the ear, but improper to the eye, 

 will affect the ear properly, but the eye not at all. 

 Again, salt is a stimulus proper to the stomach, 

 and, when it comes in contact with the membrane 

 which lines that organ, it affects its sensibility 

 agreeably and healthily ; but if you blow salt into 

 your eye, it will produce the most violent pain; yet 

 the membrane which lines the stomach is as delicate 

 in its texture as that which covers the eye. Thus, 

 again, there are certain medicines which exert their 

 influence only on certain organs. Some will act on 

 the stomach, some on the bowels only ; some on the 

 kidneys, some on the brain, some on the liver. If 

 you rub belladonna into the skin of your leg, it will 

 not affect your leg; but (excuse the bull !) you 

 will wake some fine morning, and be astonished 

 to discover that you have suddenly become blind. 

 This once occurred to a patient who was under the 

 care of the late Mr. Abernethy for a sore leg ; Mr. 

 Abernethy having ordered the sore to be dressed 

 with the extract of belladonna. The man, how- 

 ever, recovered his sight. Mr. Abernethy never 

 dressed sore legs with belladonna again. I heard 

 him relate this circumstance myself. 



