OF NATURAL HISTORY. 1S3 



Other qualities, he perceives a kind of rigidity at the tips of 

 his fingures. If the fingers are kept long in this ftate, the 

 rigidity of the nervous papillae will give him a kind of pain 

 or anxiety, which it is impoffible to defcribe. The caufe of 

 this pain is an over-diftenlion of the papillae. If a imali iu- 

 fecSt creeps on a man's hand, when the papillae arc flaccid, its 

 movements are not perceived : But if he happen? to direct 

 his eye to the animal, he immediately extends his papillae, 

 and feels diftindlly all its motions. If a body be prefent, 

 which, in the common ftate of the nerves, has fcarcely any 

 feiiiible odour, by extending the papillae of the noftrils, an 

 agreeable, dil'dgreeable, or indifferent fmell will be perceived. 

 When two perfons are whifpering, and we wifh to know 

 what is faid, we ftretch the papillae, and the other organs of 

 hearing, which are exceedingly complex. If a found is too 

 low for making an impreffion on the papillae in their natural 

 ftate of relaxation, we are apt to overftretch the organ, which 

 produces a painful or irkfome feeling. When we examine 

 a mite, or any very minute object, by the naked eye, a pain is 

 propagated over every part of that organ. Several caufes 

 may concur in producing this pain, fuch as the dilating of 

 the pupil, and the adjufting the chryftaUine lens; but the chief 

 caufe muft be afcribed to the preternatural Intumefcence and 

 extenlion of the papillae of the retina, the fubftance of which 

 is a mere congeries of nervous terminations. This circum- 

 ftance confirms a former remark, that the immediate organs 

 of fenfation were more copioufly fupplied with nervous pa- 

 pillae than thofe parts whofe ufcs require not fuch exqullite 

 Cenfibihty •, for a diftin(Slion in this refpedt is obfervable 

 even among the fenfitive organs themfelves. They are fur- 

 niflied with nerves exaiSlly proportioned to the fubtility of 

 the objecSts whofe impreflions they are fitted to receive. The 

 eye pofTelTes by far the greatefl: number. The particles of 

 light are fo minute, that, had not this wife provifion been 

 obferved in the conflru^ion of the eye, it could never have 



