( 44* ) 
between the Interfaces of the Mufcles, it will never 
form a circumfcrib’d Tumor. However, the EfFufion 
being continued per faltum thro* the ruptur’d Artery, 
will give a faint Puliation, and confequently fome Re- 
femblance of the Aneuryfm } for which Reafon it is 
by fome Chirurgeons term’d a Baftard-Aneuryfm. 
Whether or no an Aneuryfm be a Tumor form’d 
by the ‘Dilatation of the Artery, or by a Rupture of 
the internal Coats of the Artery, and a Dijienfion 
of the external , has for fome Time been a Mat- 
ter of great Difpute ; each Party protefting (perhaps 
too unjufay) againft the Poflibility of the others Opi- 
nion. 
As to the Poflibility of an Artery’s being dilated, it 
Rands fiipported by Reafon and Autopfy. We find the 
Uterine Arteries conftantly encreas’d in Thicknefs and 
Diameter, in Proportion as the Dterus is diftended ; 
and many Cafes of Palpitations of the Heart have 
been attended with great Dilatations of the Aorta ; In- 
ftances of which I have feen both in human and brute 
Subjects. 
Such a Dilatation will necefiarily follow a conftant, 
or frequent PrelTure on any Part of the Aorta , pro- 
vided fuch PrelTure does not entirely flop the progref* 
five Motion of the Blood thro’ the Aorta. 
But on the other Hand, fuch a Dilatation will al- 
ways retain fomewhat of the Form of the Artery. 
The Refifiance will not be every Way equal," as in the 
extra vafate Tumors*, becaufe the quaquaverfal Pref- 
fure of the Blood will be controll’d by the PrelTure on 
the Artery, and the Refiftance from the Coats of the 
Arteries, fo as necefiarily to form a Gyiindroeid.. 
And the Confequence of luch a Dilatation cannot (if 
con- 
