SECT. XXXII. 7. i. OF IRRITATION. 295 



month with great exaftnefs in healthy patients (and perhaps the 

 venereal orgafrn in brute animals does the fame), yet thefc pe- 

 riods do not commence either at the fyzvgies or quadratures of 

 the lunations, but at whatever time of the lunar periods they be- 

 gin, they obierve the fame in their returns till fome greater 

 caufe diiturbs them. 



. Hence, though the beft way to calculate the time of the ex- 

 peded returns of the paroxyfms of periodical difeafes is to count 

 the number of hours between the commencement of the two 

 preceding fits, yet the following obfervations may be worth at- 

 tending to, when we endeavour to prevent the returns of man- 

 iacal or epileptic difeafes ; whofe periods (at the beginning of 

 them efpecially) frequently obferve the fyzygies of the moon 

 and fun, and particularly about the equinox. 



The greateft of the two tides happening in every revolution 

 of the moon, is that when the moon approaches neareft to the 

 zenith or nadir , for this reafon, while the fun is in the northern 

 figns, that is during the vernal and fummer months, the greater 

 of the two diurnal tides in our latitude is that, when the moon 

 is above the horizon ; and when the fun is in the fouthern figns, 

 or during the autumnal and winter months, the greater tide is 

 that, which arifes when the moon is below the horizon ; and as 

 the fun approaches, fomewhat nearer the earth in winter than in 

 fummer, the greateft equinoctial tides are obferved to be a little 

 before the vernal equinox, and a little after the autumnal one. 



Do not the cold periods of lunar difeafes commence a few 

 hours before the fouthing of the moon during the vernal and 

 fummer months, and before the northing of the moon during 

 the autumnal and winter months ? Do not palfies and apoplex- 

 ies, which occu*' about the equinoxes, happen a few days before 

 the vernal equinoctial lunation, and after the autumnal one ? 

 Are not the periods of thofe diurnal difeafes more obftinate, 

 that commence many hours before the fouthing or northing of 

 the moon, than of thofe which commence at thofe times ? Arc 

 not r'" les and apoplexies more dangerous which com- 



mence many days before the fyzygies of the moon, than thofe 

 whicJ: happen at thofe times ? See Sect. XXXVI. on the peri- 

 ods of '!-T;ufes. 



VII. Another very frequent caufe of the cold fit of fever is 

 the quiefcence of fome of thofe large congeries of glands, which 

 compofe the liver, fpiecn, or pancreas ; one or more of which 

 are frequently fo enlarged in the autumnal intermittents as to 

 be perceptible to the touch externally, and are called by the vul- 

 gar ague-cakas. As thefe glands are (limulated into acYion by 

 the fpecific pungency of the fluids, which they abforb, the gener- 

 al 



