242 ESSAYS AND OBSERVATIONS 



been a former relaxation or predifpofition 

 in the veflels to fuffer themfelves to be di- 

 lated, otherwife aneurifms iliould often 

 be obferved in high fevers, and after am- 

 putations of the larger extremities. 



In many cafes there feeins to be fomc 

 caufe, which we canno'c afcertain either 

 from the habit of body, or from any 

 particular flruclure or diforder of the 

 parts cbferved after death. Sometimes 

 a fcorbutic or venereal taint, or fome o- 

 ther acrimony in the blood, has been ac- 

 cufed ; at other times, particular obflruc- 

 tions or difeafes of the arteries, at the 

 part where they were dilated, have* been 

 faid to occafion them. And certainly, 

 there mud either be a particular difpofi- 

 tion of the blood, which renders it capa- 

 ble of foftning or relaxing the arterial 

 fibres, or fome diforder in the fibres or 

 veifels affecfled, or a particular quality 

 in the fluids thrown upon fuch parts, be- 

 fore an aneurifm can be produced j tho* 

 thefe caufes may be too fubtile to come 

 Vinder the obiervation of our fenfes ; for, 



how 



