363 



HITCHCOCK'S ANATOMY 



temperature is always agreeable, but painful if much in- 

 creased. Many odors snuffed in small quantity are pleasant, 

 but when given to satiety, become disgusting. The probable 

 design of this provision seems to be to prevent injury by an 

 inordinate stimulation of any of the nerves. For instances are 

 on record, where the mucous membrane of the nostrils has 

 been severely affected by the fumes of ammonia given in 

 fainting. 



675. Habit makes painful Sensations pleasant —It 

 is a curious but interesting fact that the pain excited by un- 

 accustomed sensations may sometimes be exchanged for its 

 opposite, after the system has become habituated to them. 

 Thus tobacco and alcoholic liquors are at first disagreeable to 

 most persons ; but when the disgust has been overcome by 

 any means a love for them succeeds, and generally a strong 

 craving for excessive indulgence also. 



676. Nerves of Special Sense can perform bit one 

 Function. — The nerves of special sense are incapable of per- 

 forming any function except that for which they were orig- 

 inally designed. Thus the optic nerve can perform the func- 

 tion of vision only, the olfactory only that of smelling, and 

 the auditory only that of hearing. 



677. Effect of Belief on our Sensation s— The effect 

 of previous belief in modifying our sensations, is shown in 

 the two cases copied from Carpenter's Physiology. "A 

 clergyman told me that some time ago suspicions were enter- 

 tained in his parish, of a woman who was supposed to have 

 poisoned her newly born infant. The coffin was exhumed, 

 and the procurator fiscal, who attended with the medical men 

 to examine the body, declared that he already perceived the 

 odor of decomposition, which made him feel faint, and in con- 

 sequence he withdrew. But on opening the coffin, it was 



What instance of this from odors? 675. How does habit sometimes affect painful sen- 

 sations? What examples ? 676. What is said of the function of the nerves of special 

 eense ? 677. How does our belief affect our sensations? Give the instance of the infant. 



