134 DISEASES CLASS I. 2- 5. 1. 



ORDO II. 



Decreased Irritation, 



GENUS V. 



Decreased Jlclion of the Organs of Sense, 

 SPECIES. 



1. Stultitia mirritabilitas. Folly from imrritability. Dulness 

 of perception. When the motions of the fibrous extremities of 

 the nerves of sense are too weak, to excite sensation with suf- 

 ficient quickness and vigour. The irritative ideas are neverthe- 

 less performed, though perhaps in a feeble manner, as such peo- 

 ple do not run against a post, or walk into a well. There are 

 three other kinds of folly; that from deficient sensation, from 

 deficient volition, and from deficient association, as will be men- 

 tioned in their places. In delirium, reverie, and sleep, the 

 power of perception is abolished from other causes. 



2. Viscus imminutus. Diminished vision. In our approach to 

 old age our vision becomes imperfect, not only from the form of 

 the cornea, which becomes less convex, and from its decreased 

 transparency mentioned in Class I. 1. 3. 14; but also from the 

 decreased irritability of the optic nerve. Thus, in the inirritative 

 or nervous fever, the pupil of the eye becomes dilated; which in 

 this, as well as in the dropsy of the brain, is generally a fatal 

 symptom. A part of the cornea as well as a part of the albugi- 

 nea in these fevers is frequently seen during sleep; which is 

 owing to the in irritability of the retina to light, or to the gene-? 

 ral paresis of muscular action, and in consequence to the less 

 contraction of the sphincter of the eye, if it may be so called, at 

 that time. 



In some eyes there is an inaptitude to adapt themselves to 

 the perception of objects at different distances, which I suppose 

 may be owing to the inirritability of those muscular fibres, which 

 constitute the ciliary process, so well described and explained by 

 Dr. Porterfield, and in the Scots Medical Essays, and so elegant- 

 ly seen in a dissected eye. It was formerly believed, and has in- 

 deed lately been again pretended, that the focus of the crystal- 

 line humour was adapted to objects at different distances by a 

 change of the shape of the whole eye by the action of the exter- 

 nal muscles, which are inserted into the tunica albuginea, and 

 give motion to it in every direction; but in answer to this may be 



