XXXII. 2. i. OF IRRITATION. . iS 2 : 



quantity of fenforial power, another kind of fever arifes-, which 

 may be termed, Typhus irritativus, or Febris irritativa pulfu de- 

 bili, or irritative fever with weak pulfe. The former of thefe 

 fevers is the fynocha of nofologifts, and the latter the typhus mi- 

 tior, or nervous fever. In the former there appears to be an 

 increafe of fenforial power, in the latter a deficiency of it ; 

 which is (hewn to be the immediate caufe of ftrength and weak- 

 nefs, as defined in Se£t. XII. i. 3. 



It mould be added, that a temporary quantity of ftrength or 

 debility may be induced by the defect or excefs of ftimulus above 

 what is natural ; and that in the fame fever debility always exifls 

 during the cold jit, though Jlrength does not always exijl during the 

 hot fit. 



Thefe fevers are always connected with, and generally indu- 

 ced by, the difordered irritative motions of the organs of fenfe, 

 or of the inteftinal canal, or of the glandular fyftem, or of the 

 abforbent fyftem ; and hence are always complicated with fome 

 or many of thefe difordered motions, which are termed the fymp- 

 toms of the fever, and which compofe the great variety in thefe 

 difeafes. 



The irritative fevers both with ftrong and with weak pulfe, 

 as well as the fenfitive fevers with ftrong and with weak pulfe, 

 which are to be defcribed in the next fection, are liable to peri- 

 odical remiflions, and then they take the name of intermittent 

 fevers, and are diftinguifhed by the periodical times of their 

 accefs. 



II. For the better illuftration of the phenomena of irritative 

 fevers we mud refer the reader to the circumftances of irritation 

 explained in Seel:. XII. and fhall commence this intricate fubjedc 

 by fpeaking of the quick pulfe, and proceed by confidering many 

 of the caufes, which either feparately or in combination molt 

 frequently produce the cold fits of fevers. 



1. If the arteries are dilated but to half their ufual diameters, 

 though they contract twice as frequently in a given time, they 

 will circulate only half their ufual quantity of blood : for as 

 they are cylinders, the blood which they contain muft be as the 

 fquares of their diameters. Hence when the pulfe hecomes- 

 quicker and fmaller in the fame proportion, the heart and arte- 

 ries act with lefs energy than in their natural ftate. See Sect. 

 XII. 1. 4. 



That this quick fmall pulfe is owing to want of irritability, 

 appears, firft, becaufe it attends other fymptoms of want of ir- 

 ritability ; and, fecondly, becaufe on the application of a ftimu- 

 lus greater than ufual, it becomes flower and larger. Thus in 

 cold fits of agues, in hyfteric palpitations of the heart, and when 



the 



