SECT. XII. r. OF STIMULUS AND EXERTION. 71 



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 contrac- 

 tion in health is greater as nine to fix, or as three 

 to two. 



On the contrary in inflammatory difeafes with 

 ftrength, as in the pleuriiy, 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 diameter of the 

 artery in diaftole be one third greater than in 

 health, which I believe is near the truth, the re* 

 fult will be, that the velocity of the contractile fides 

 of the arteries will be in a pleurify as two and a half 

 to one, compared to the velocity of their contrac- 

 tion in a ftate of health, for if the circumference 

 of the fyftole of the artery be three lines, and the 

 diaftole in health be twelve lines in circumference, 

 and in a pleurify eighteen lines ; and fecondly, if 

 the artery pulfates thrice in the difeafed ftate for 

 twice in the healthy onc it follows, that the velo- 

 city of contraction in the difeafed ftate to that in 

 the healthy ftate will be forty-five to eighteen, or as 

 two and a half to one. 



From hence it would appear, that if we had a 

 criterion to determine the velocity of the arterial 

 contractions, it would at the fame time give us their 

 ftrength, and thus be of more fervice in diftinguifh- 

 ing difeafes, than the knowledge of their fre- 

 quency. As fuch a criterion cannot be had, the 

 frequency of puifauon, the age of the patient being 

 allowed for, will in ibme meafure affift us to diftin- 

 guifli arterial ftrength from arterial debility, fince 

 in inflammatory difeafes with ftrength the frequency 

 feldotn exceeds one hundred and eighteen or one 



hundred 



