374 DISEASES CLASS IV. 1. 2. 2. 



lates the surface of the eye, at the same time the increased abun- 

 dance of tears stimulates the puncta lachrymalia into greater ac- 

 tion; and the fluid thus absorbed stimulates the lachrymal sac, 

 and its nasal duct in the nose into greater action. In a contrary 

 direction of this chain of association the present increase of 

 action is induced. First, the nasal duct of the lachrymal sac is 

 excited into increased action by some pleasurable or painful idea, 

 as described in Sect. XVI. 8. 2. 2d. The puncta lachrymalia 

 or other extremity of the lachrymal sac sympathizes with it (as 

 the two ends of all other canals sympathize with each other.) 

 3d. With these increased motions of the puncta lachrymalia those 

 of the excretory duct of the lachrymal gland are associated from 

 their having so perpetually acted together. And, lastly, with 

 the increased actions of the excretory duct of this gland are as- 

 sociated those of the other end of it by their frequently acting 

 together; in the same manner as the extremities of other ca- 

 nals are associated, and thus a greater flow of tears is poured 

 into the eye. 



When a flow of tears is produced in grief, it is believed to 

 relieve the violence of it, which is worthy a further inquiry. 

 Painful sensations, when great, excite the faculty of volition; 

 and the person continues voluntarily to call up or perform those 

 ideas, which occasion the painful sensation; that is, the afflicted 

 person becomes so far insane or melancholy; but tears are 

 produced by the sensorial faculty of association, and shew that 

 the pain is so far relieved as not to excite the excessive power of 

 volition, or insanity, and are therefore a sign of the abatement of 

 the painful state of grief, rather than a cause of that abatement, 

 gee Class III. 1.2.10. 



2. Sternutatio a lumine. Some persons sneeze from looking 

 up at the light sky in a morning after coming out of a dark 

 bed room. The olfactory nerves are brought into too great ac- 

 tion by their sympathy with the optic nerves, or by their respec- 

 tive sympathies with some intervening parts, as probably with 

 the two extremities of the lachrymal sac; that is, with the punc- 

 ta lachrymalia and the nasal duct. See Class II. 1, 1. 3. 



3. Dolor dentium a stridore. Tooth-edge from grating sounds, 

 and from the touch of certain substances, and even from ima- 

 gination alone, is described and explained in Sect. XVI. 10. 

 The increased actions of the alveolar vessels or membranes are 

 associated with the ideas, or sensual motions of the auditory 

 nerves in the first case; and of those of the sense of touch, in 

 the second case, and by imagination, or ideas exerted of painful 

 sensation alone, in the last. 



4. Risus sardonic:^ A disagreeable smile attends inflammations 



