434 DISEASES OF IRRITATION. SECT. XXXU. p. 



cumftances of cold, inanition, or lunation, which 

 immediately caufed them. 



' v We muft, however, oWerve, that the periods of 

 quiefcence and exacerbation in difeafes do not 

 always commence at the time&'of the fyzygies or 

 'quadratures of the' moon and fun, or at the times 

 of their pafling the zenith or nadir; but as it is 

 probable, that the ftimulus of the particles of the 

 circumfluent blood is gradually diminifhed from 

 the time of the quadratures to that of the fyzy- 

 gies, 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 recur at the fame 

 'periods 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 difTevered links of the lunar or folar cir- 

 cles of animal a&ion. 



In this mariner the periods of menftruation obey 

 the lunar month with great exadtnefs in healthy pa- 

 tients (and perhaps the venereal orgafm in brute 

 animals does the fame), yet tjiefe periods do not 

 commence ' either at the fyzygies or quadratures 

 t)f the lunations/ but at whatever time of the lunar 

 periods they begin, they obferve the fame in their 

 returns till fome greater caufe diflurbs them. 



Hence, though the bell way to calculate the time 

 of the expected returns of the paroxyfms of peri- 

 odical difeafes is to count the number of hours 

 between the commencement of the two preceding 

 fits, yet the following obfervations may be worth 

 attending to, when we endeavour to prevent the 

 returns of maniacal or epileptic difeafes ; whofe 

 periods (at the beginning of them efpecially) fre- 

 quently obferve the fyzygies of the moon an4 

 'fun, and particularly about the equinox. 



The greateft of the two tides happening in every 

 , * *-M revolution 



