[ 3?2 ] 
caufe its coagulation in thofe true aneuryfms, which 
are attended with a‘ pouch, are owing*'? For in fuch 
enlargements a part of the blood is without motion, 
which will congeal when at reft, and in contadl with 
the lack ; and thus one layer may be formed ; and 
the fack afterwards enlarging, another portion of the 
blood will then be at reft ; and fo a fecond layer 
may be formed; and thence probably is the origin of 
thofe laminated thrombi met with in fuch facks. 
Likewife, to the blood being at reft, is probably 
owing its coagulation in the large arteries which are 
tied after amputation, or other operations; for after 
moft of fuch ligatures there will be a part of the 
artery impervious, in which the blood can have no 
motion. The coagulim after amputation might in- 
deed be fuppofed owing to air ; but, confidering the 
manner in which arteries are tied whilft the blood 
is flowing from them, it does not feem probable that 
the air has any effetft on what is above the ligature. 
To the blood’s being without motion in the cavity 
of the uterus , is its coagulation therein probably 
owing ; hence the origin of thofe large clots which 
we fometimes obferve to come from this cavity, and 
which, when they are more condenfed by the ouzing 
out of the ferum, and of the red particles, affume 
a llefh-like appearance, and have often been called 
moles or falfe conceptions. 
In Experiment the 5th, we found that the blood 
could be frozen and thawed again, without being 
coagulated: this, likewife is an experiment which 
* An inftance of which may be feen in the Medical Obf. and 
Inq. vol. i. article xxvii. fig. iii. 
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