35<5 PERIODS Sect. XXXVI. 3. a, 



conftitutions ar.e liable to get into better fpirits at the aecefs of 

 the hot fit of this evening fever ; and are thence inclined to fit 

 up late ; which by further enfeebfing them increafes the dif- 

 eafe ; whence they lofe their ftrength and their colour. 



Hence delicate ladies, who do not ufe rouge, are obferved to 

 become paler in the evening ; which is probably owing to the 

 circulation through the whole fyftem being lefs frequently per- 

 formed in a given time, though the pulfe is quicker *, and hence 

 the mafs of blood becomes lefs frequently oxygenated in the 

 lungs, and in confequence has a lefs florid colour. This pale 

 colour therefore arifes from debility, which occurs to delicate 

 people in the evening from the exhauftion of fenforial power 

 during the day, and is generally attended by quicknefs of pulfe ; 

 by which circumftance the debility may in fome degree be 

 meafured. 



Another caufe of the colour of the fkin may occafionally de- 

 pend on the increafed action of the cutaneous capillaries, as in 

 the hot fit of fever; or by the production of new blood veffels, 

 as in topical inflammations. And palenefs may arife from the 

 contrary fituations, as from inaction of the cutaneous capillaries 

 in the cold paroxyfm of fever, and from the concretion of the 

 fides of the fmall cutaneous arteries, as in old age. 



2. The periods of hectic fever, fuppofed to arife from ab- 

 forption of matter, obey the diurnal periods like the above, 

 having the cxacerbefcence towards evening, and the remif- 

 fion early in the morning, with fweats, or diarrhoea, or urine 

 with white fediment. 



3. The periods of quotidian fever are either catenated with 

 folar time, and return at the intervals of twenty-four hours; or 

 with lunar time, recurring at the intervals of about twenty-five 

 hours. There is great ufe in knowing with what circumftances 

 the periodical return or new morbid motions are conjoined, as 

 the mod: effectual times of exhibiting the proper medicines are 

 thus determined. So if the torpor, which ufhers in an ague fit, 

 is catenated with the lunar day ; it is known when the bark or 

 opium muft be given, fo as to exert its principal effect about the 

 time of the expected return. Solid opium mould be given about 

 an hour before the expected cold fit ; liquid opium and wine 

 about half an hour ; the bark repeatedly for fix cr eight hours 

 previous to the expected return. 



4. The periods of tertian fevers, reckoned from the com- 

 mencement of one cold fit to the commencement of the next 

 •cold fit, recur with folar intervals of forty-eight hours, or with 

 lunar ones of about fifty hours. When the recurrence of thefe 

 begins one or two hours earlier than the folar period, it fhews, 



that 



