43 OF STIMULUS Slct. XII. i. . 



received at each interval of the activity of the fibres. Hence in 

 repeated motions, as of the fingers in performing on the harpfi- 

 chord, it would at firft fight appear, that fwiftuefs and ftrength 

 were incompatible ; nevertheiefs the iingle contraction of a inuf- 

 cle is performed with greater velocity as well as with greater 



:ce by vigorous conftitutions, as in throwing a javelin. 



There is however another circumftance, which may often 

 contribute to caufe the quicknefs of the pulfe in nervous fevers, 

 as in animals bleeding to death in the flaughter-houfe ; which is 

 the deficient quantity of blood 5 whence the heart is but half 

 diftended, and in confequence fooner contracts. See Seel:. 

 XXXII. 2. r. 



For we mud not confound frequency of repetition with 

 quicknefs of motion, or the number of pulfations with the ve- 

 locity, with which the fibres, which conftitute the coats of the 

 arteries, contract themfelves. For where the frequency of the 

 pulfations is but ieventy-five in a minute, as in health ; the con- 

 tracting fibres, which conftitute the fides of the arteries, may 

 move through a greater fpace in a given time, than where the 

 frequency of puliation is one hundred and fifty in a minute, as 

 in fome fevers with great debility. For if in thofe fevers the 

 arceries do not expand themfelves in their diaftole to more than 

 half the ufual diameter of their diaftole in health, the fibres 

 which conftitute their coats, will move through a lefs fpace in 

 a minute than in health, though they make two pulfations for 

 c.ie. 



Suppofe the diameter of the artery during its fyftole to be- 

 cne line, and that the diameter of the fame artery during its di- 

 aftole is in health four lines, and in a fever with great debility 

 only two lines. It follows that the arterial fibres Contract in 

 health from a circle of twelve lines in circumference to a circle 

 of three lines in circumference, that is they move through a fpace 

 of nine lines in length. While the arterial fibres in the fever 

 with debility would twice contract from a circle of fix lines to a 

 circle of three lines ; that is while they move through a fpace 

 equal to fix lines. Hence though the frequency of pulfation 

 in fever be greater as two to one, yet the velocity of contract 

 lion in health is greater as nine to fix, eras three to two. 



On the contrary in inflammatory difeafes with ftrength, as in 

 the pleurify, the velocity of the contracting fides of the arteries 

 is much greater than in health : for if we fuppofe the number of 

 pulfations in a pleurify to be half as much more than in health, 

 that is as one hundred and twenty to eighty, (which is about 

 what generally happens in inflammatory difeafes) and if the di- 

 a ..- ter of the artery in diaftoie^e one third greater than in 



* health, 



