CG PROPERTIES OF 



mine, by experiment, whether the ligature being a longer or 

 shorter time upon the arm, even in the ordinary way of bleed- 

 ing, might not influence this appearance of the blood. And 

 accordingly, in the presence of Dr. Drummond, Mr. Field, Mr. 

 Hendy, and Mr. Cockson, I made the following experiment : 



EXPERIMENT XXXII. 



On the 9th of October, I tied up both the arms of a healthy 

 young man with a degree of tightness sufficient to make the 

 veins swell and become turgid, whilst the pulse remained free; 

 a vein in one arm was opened immediately after making the 

 ligature, and an ounce of blood was received into a cup. I 

 chose to take away so small a quantity that there might be the 

 less probability of producing any change upon the blood by 

 weakening the body. The ligature was left upon the other 

 arm for an hour, which made the veins very turgid, and like- 

 wise made the person complain of a stiffness in his fore-arm ; 

 the artery in his wrist being felt all the time, but less distinctly 

 than in the other arm which was without a ligature. At the 

 end of an hour this vein was opened, the orifice was large, and 

 an ounce of blood was taken away. Upon attending carefully 

 to each cup, it did appear that the ligature had produced some 

 change; for in the first place, the blood which had been so 

 long detained in the arm by the ligature was darker coloured 

 (xxxi), or blackish, whilst that from the other arm was more 

 florid, even at its first running from the vein. 2dly. The blood 

 that had been so long in the arm was rather later in being 

 coagulated ; for it did not begin to part with its serum till at 

 the end of thirty-seven minutes after puncturing the vein; 

 whilst in the other the coagulation was completed, and the 

 serum was beginning to ooze out in thirty minutes. 3dly. The 

 blood which was first taken away was without a size, whilst 

 that which had been so long in the other arm had a small 

 spot about the breadth of a silver penny, and did not cover a 

 twentieth part of the surface. 



From this experiment, therefore, it would seem that a liga- 

 ture long continued may produce a size, agreeably to Dr. 



(xxxi.) The darkening of blood by its stagnation in the living body, 

 is mentioned in Note v. 



