294 DISEASES Sect. XXXII. 6. i. 



effects on the organs of fenfe adapted to the perception of them, 

 as of vibration on the auditory nerves, we {hall ceafe to be fur- 

 prifed, that fo minute a diminution in the gravity of the parti- 

 cles of blood mould fo far affect their chemical changes, or their 

 itimuhting quality, as, joined with other caufes, fometimes to 

 produce the beginnings of difeafes. 



Add to this, that if the lunar influence produces a very fmall 

 degree of quiefcence at firft, and if that recurs at certain peri- 

 ods even with lefs power to produce quiefcence than at firft, yet 

 the quiefcence will daily increafe by the acquired habit acting 

 at the fame time, till at length fo great a degree of quiefcence is 

 induced as to produce phrenfy, canine madnefs, epilepfy, hyfter- 

 ic pains or cold fits of fever, inftances of many of which are to 

 be found in Dr. Mead's work on this fubje£t. The folar influ- 

 ence alfo appears daily in feveral difeafes •, but as darknefs, fi- 

 lence, fleep, and our periodical meals mark the parts of the fo- 

 lar circle of actions, it is fometimes dubious to which of thefe 

 the periodical returns of thefe difeafes are to be afcribed. 



As far as I have been able to obferve, the periods of inflam- 

 matory difeafes obferve the folar day ; as the gout and rheuma- 

 tifm have their greatelt quiefcence about noon and midnight, 

 and their exacerbations fome hours after ; as they have more 

 frequently their immediate caufe from cold air, inanition, or fa- 

 tigue, than from the effects of lunations : whilft the cold fits of 

 hyfteric patients, and thofe in nervous fevers, more frequently 

 occur twice a day, later by near half an hour each time, accord- 

 ing to the lunar day ; whilft fome fits of intermittents, which 

 are undifturbed by medicines, return at regular folar periods, 

 and others at lunar ones •, which may, probably, be owing to the 

 difference of the periods of thofe external circumftances of cold, 

 inanition, or lunation, which immediately caufed them. 



We muft, however, obferve, that the periods of quiefcence 

 and exacerbation in difeafes do not always commence at the times 

 of the fyzygies or quadratures of the moon and fun, or at the 

 times of their palling the zenith or nadir ; but as it is probable, 

 that the flimulus of the particles of the circumfluent blood is 

 gradually diminifiied from the time of the quadratures to that of 

 the fyzygies, the quiefcence may commence at any hour, when 

 co-operating with other caufes of quiefcence, it becomes great 

 enough to produce a difeafe : afterwards it will continue to re- 

 cur at the fame period of the lunar or folar influence ; the fame 

 caufe operating conjointly with the acquired habit, that is with 

 the catenation of this new motion with the diffevered links of 

 the lunar or folar circles of animal adlion. 



In this manner the periods of menilruation obey the lunar 



month 



