35 » DISEASES Sect. XXXV. 2. 3. 



creafed motion of its fibres, fo far diminifhes or exhaufts the fen- 

 ibrial power of fenfation ; that the primary part of the train be- 

 ing lefs fenfible ceafes both to feel pain, and to acl: with un- 

 natural energy. 



3. Examples of the third mode, where the primary part of a 

 train of fenfitive aflbciation of motions may experience increafed 

 fenfation, and the fecondary part increafed action, are like wife 

 not unfrequent j as it is in this manner that mod inflammations 

 commence. Thus, after Handing fome time in fnow, the feet 

 become affected with the pain of cold, and a common coryza, 

 or inflammation of the membrane of the noftrils, fucceeds. It 

 is probable that the internal inflammations, as pleurifies, or he- 

 patitis, which are produced after the cold paroxyfm of fever, 

 originate in the fame manner from the fympathy of thofe parts 

 with fome others, which were previoufly pained from quief- 

 cence ; as happens to various parts of the fyftem during the cold 

 fits of fevers. In thefe cafes it would feem, that the fenforial 

 power of fenfation becomes accumulated during the pain of cold, 

 as the torpor of the vefTels occafioned by the defect; of heat con- 

 tributes to the increafe or accumulation of the fenforial power of 

 irritation, and that both thefe become exerted on fome internal 

 part, which was not rendered torpid by the cold which affected 

 the external parts, nor by its aflbciation with them ; or which 

 fooner recovered its fenfibility. This requires further con- 

 fideration. 



4. An example of the fourth mode, or where the primary 

 part of a fenfitive aflbciation of motions may have increafed ac- 

 tion, and the fecondary part increafed fenfation, may be taken 

 from the pain of the fhoulder, which attends inflammation of the 

 membranes of the liver, fee Oafs IV. 2. 2. 9. ; in this circum- 

 fiance fo much fenforial power feems to be expended in the vio- 

 lent actions and fenfations of the inflamed membranes of the 

 liver, that the membranes aflbciated with them become quief- 

 cent to their ufual ilimuli, and painful in confequence. 



There may be other modes in which the primary and feconda- 

 ry parts of the trains of aflbciated fenfitive motions may recipro- 

 cally affect, each other, as may be fcen by looking over Clafs IV. 

 in the catalogue of difeafes ; all which may probably be refolved 

 into the plus and minus of fenforial power, but we have not yet 

 had fuiheient obfervations made upon them with a view to this 

 doctrine. 



III. The aflbciated trains of our ideas may have fympathies, 

 and their primary and fecondary parts affect, each other in fome 

 manner fimilar to thofe above defcribed ; and may thus occafion 

 various curious phenomena not yet adverted te, befides thofe ex- 

 plained 



