SECT. XII. 3. 6. AND EXERTION. 61 



cold paroxyfm of fever is completely formed. See Sect. XVII. 

 3. 3. on Catenation of Animal Motions. 



6 If a ftimulus, which at firft excited rhe affected organ into 

 fo great exertion as to produce fenfation, be continued for a 

 certain time, it will ceafe to produce fenfation both then and 

 when repeated, though the irritative motions in confequence of 

 it may continue to be re-excited. 



Many catenations of irritative motions were at firft fucceed- 

 ed by fenfarion, as the apparent motions of objects when we 

 walk paft them, and probably the vital motions themfelves in 

 the early ftate of our exiftence. But as thofe fenfations were 

 followed by no movements of the fyftem in confequence of 

 them, they gradually ceaied to be produced, not being joined to 

 anv fucceeding link of catenation. Hence contagious matter, 

 which has for fome weeks ftimulated the fyftem into great and 

 permanent fenfation, ceafes afterwards to produce general fenfa- 

 tion, or inflammation, though it may (till induce topical irrita- 

 tions. See Sed XXXIII. 2. 8. XIX 10. 



Our abforbent fyftem then feems to receive thofe contagious 

 matters, which it has before experienced, in the fame manner as 

 it imbibes common moifture or other fluids ; that is, without 

 being thrown into fo violent action as to produce fenfation ; the 

 confequence of which is an increafe of daily energy or activity, 

 till inflammation and its confequences fucceed. 



7. If a ftimulus excites an organ into fuch violent contrac- 

 tions as to produce fenfation, the motions of which organ had 

 not ufually produced fenfation, this new fenforial power, added 

 to the irritation occafioned by the ftimulus, increafes the activ- 

 ity of the organ. And if this activity be catenated with the di- 

 urnal circle of actions, an increafing inflammation is produced ; 

 as in the evening paroxyfms of fmall-pox, and other fevers with 

 inflammation. And hence fchirrous tumours, tendons and 

 membranes, and probably the arteries themfelves become in- 

 flamed, when they are ftrongly ftimulated. 



IV. Of Stimulus greater than natural. 



i. A quantity of ftimulus greater than natural, producing an 

 increafcd exertion of fenforial power, whether that exertion be 

 in the mode of irritation, fenfation, volition, or aflbciation, dimin- 

 ifhes the general quantity of it. This fact is obfervable in the 

 progrefs of intoxication, as the increafed quantity or energy of 

 the irritative motions, owing to the ftimulus of vinous fpirit, in- 

 troduces much pleafurable fenfation into the fyftem, and much 

 exertion of muicular or fenfual motions in confequence of this 



increafed 



