THE BLOOD. 25 



in different diseases. For though the blood of a person in 

 health is completely coagulated in seven minutes after it is 

 taken out of the veins, yet in some diseases, I have found the 

 blood fifteen or twenty minutes, nay, even an hour and a half, 

 before it was completely jellied. 



As we see in the above-related experiments, that the blood 

 coagulates in the body when suffered to rest for a little time, 

 is it not probable that to this cause its coagulation in those 

 true aneurisms, which are attended with a pouch, are owing ? l 

 For in such enlargements a part of the blood is without mo- 

 tion, which will congeal when at rest, and in contact with the 

 sac ; and thus one layer may be formed ; and the sac afterwards 

 enlarging, another portion of the blood will then be at rest ; 

 and so a second layer may be formed ; and thence probably is 

 the origin of those laminated coagula met with in such sacs. 



Likewise, to the blood's being at rest, is probably owing its 

 coagulation in the large arteries which are tied after amputa- 

 tion, or other operations ; for after most of such ligatures there 

 will be a part of the artery impervious, in which the blood can 

 have no motion. The coagulum after amputation might in- 

 deed be supposed owing to air ; but, considering the manner 

 in which arteries are tied whilst the blood is running from 

 them, it does not seem probable that the air has any effect on 

 what is above the ligature. 



To the blood's being without motion in the cavity of the 

 uterus, is its coagulation th'erein probably owing; hence the 

 origin of those large clots which sometimes come from that 

 cavity ; and which, when more condensed by oozing out of the 

 serum, and of the red globules, assume a flesh-like appearance, 

 and have often been called moles or false conceptions. 



In Experiment the Fifth, we found that the blood could be 

 frozen and thawed again, without being coagulated : this like- 

 wise is an experiment which I have repeated .several times, 

 that I might be sure of the fact. I have also varied the experi- 

 ment by sometimes putting the vein into a phial of water, and 

 freezing the whole in a solution of sal ammoniac in snow; and 

 sometimes I have put the vein into the solution itself; and 



1 An instance of which may be seen in the Med. Obs. and Inq. vol. i, article xxvii, 

 fig. iii. 



