56 PROPERTIES OF 



2dly. It may be observed, that the great difficulty in admit- 

 ting the conclusion made in the former part of these sheets 

 (viz. that the want of size in the last cup is occasioned by an 

 alteration in the blood-vessels) was to conceive how these vessels 

 could possibly alter the properties of the lymph so suddenly, as 

 in the time between receiving the blood into the first cup and 

 into the last. But this case confirms that inference, by showing 

 the fact in a clearer point of view ; for even here, where the 

 appearance of the size was reversed, it was found that the blood 

 which had a crust or size was latest in coagulating, and that it 

 was this blood which was taken out of the vessels when they 

 acted most strongly, as was proved by the rapidity with which 

 it flowed into the cup. 



3dly. Since the times in which the blood jellied in these 

 cups were so very different (the first coagulating in twelve mi- 

 nutes, the second in about twenty-two, the third in thirty-five, 

 and the fourth in less than three minutes, notwithstanding 

 these cups were filled in less than two minutes after one another), 

 it shows, I say, how soon that state of the blood-vessels on 

 which the size depends, can be removed and assumed, and 

 therefore leads us to conclude, that although this size is in 

 general a sign of an inflammatory disorder, or a strong action 

 of the vessels (see Notes xxm and xxiv), yet there may be several 

 circumstances to be taken into the account, before we can judge 

 from its presence, or absence, whether or no venesection should be 

 repeated: and it likewise shows clearly, that it would be improper 

 to determine, from the presence of this alone, when bleeding is 



nation, that the vessels were acting more weakly whilst the second or third cups were 

 filled. For so easily does this size appear to be removed, or formed, that I suspect 

 it may sometimes happen that when the blood is taken away in a full stream, from 

 a large orifice, the patient may be so suddenly weakened, and the properties of the 

 blood may in consequence be so changed by the time the second cup is filled, that 

 the size shall be removed ; and yet afterwards the vessels may recover their former 

 tone, so that the third or fourth cup may acquire a size again. Nay, I suspect that 

 this appearance may even be affected by the passions, particularly from observing 

 that the patient above mentioned, as well as others whose blood at first trickled 

 slowly down their arms, had been much afraid of the lancet (xxvin). 



(xxvin.) See Note xxiv. Some interesting speculations on the pro- 

 bable modifications in the nature of the current of blood under different 

 degrees of vital action, are given in Dr. Davy's Researches, vol. ii, p. 83. 



