X50 CATENATION Sect. XVII. 3. 2. 



motion, have the ftrongeft connexion. Thirdly, that of thefe, 

 thofe, which were firft formed, have the ftrongeft: connexion. 

 Fourthly, that if an animal motion be excited by more than one 

 caufation, aflbciation, or catenation, at the fame time, it will be 

 performed with greater Energy. 



2. Hence alfo we underftand, why the catenations of irrita- 

 tive motions are more ftrongly connected than thofe of the oth- 

 er clafles, where the quantity of unmixed repetition has been 

 equal ; becaufe they were firft formed. Such are thofe of the i 

 fccerning and abforbent fyftems of veffels, where the action of 

 the gland produces a fluid, which ftimulates the mouths of its 

 correfpondent abforbents. The aflbciated motions feem to be 

 the next moft ftrongly united, from their frequent repetition ; \ 

 and where both thefe circumftances unite, as in the vital motions,! 

 their catenations are indiflbluble but by the deftruction of the 

 animal. 



3. Where a new link has been introduced into a circle of 

 actions by fome accidental defect: of ftimulus ; if that defect: of 

 ftimulus be repeated at the fame part of the circle a fecond or 

 a third time, the defective motions thus produced, both by the 

 repeated defect of ftimulus and by their catenation with the 

 parts of the circle of actions, will be performed with lefs and 

 kfs energy. Thus if any perfon is expofed to cold at a certaiit 

 hour to-day, fo long as to render fome part of the fyftem for 

 a time torpid ; and is again expofed to it at the fame hour to-j 

 morrow, and the next day ; he will be more and more arTectedl 

 by it, till at length a cold fit of fever is completely formed, as] 

 happens at the beginning of many of thofe fevers, which arcl 

 called nervous or low fevers. Where the patient has flight pe-J 

 riodical fhiverings and palenefs for many days before the febrile 

 paroxyfm is completely formed. 



4. On the contrary if the expofure to cold be for fo fhort a 

 time, as not to induce any confiderable degree of torpor or qui-) 

 efcence, and is repeated daily as above mentioned, it lofes itsf 

 effect more and more at every repetition, till the conftitution 

 can bear it without inconvenience, or indeed without beinrr con- 

 fcious of it. As in walking into the cold air in frofty weather* 

 The fame rule is applicable to increafed ftimulus, as of heat, or 

 vinous fpirit, within certain limits, as is applied in the two laft 

 paragraphs to Deficient Stimulus, as is further explained in Sc 

 XXXVI. on the Periods of Difeafes. 



5. Where irritation coincides with fenfation to produce the 

 • catenations of motion, as in inflammatory fevers, they are 



t -xited with ftill greater energy than by the irritation alone. 



... - tickled in play, bv a feather light- 



