THE BLOOD. 49 



means we may judge what effect the evacuation has produced 

 on the strength or fulness of the vessels ; and may, perhaps, by 

 inspecting the last cup, especially if it contains only a small 

 quantity, be able to guess pretty nearly at the nature of the 

 blood which remains in the body. In the rheumatic case men- 

 tioned in page 35, every cup contained this crust : and although 

 the blood in the last cup coagulated in much less time than 

 that in the first, yet, as it was later in coagulating than common, 

 I suspected what remained in the vessels had the same dispo- 

 sition ; but the patient recovered without repeating the evacua- 

 tion. 



It may be mentioned here, that I have once or twice seen 

 blood which, when it first began to coagulate, had on its sur- 

 face a red pellicle, and underneath a transparent fluid, which 

 afterwards formed a crust. In these cases, if the red pellicle 

 had not been removed before the rest of the blood had con- 

 gealed, we might have concluded that no part of the blood had 

 this disposition to form a white crust. This appearance, I 

 should imagine, was owing to the blood, where in contact with 

 the air, having coagulated before the red particles had time to 

 subside from that part of the lymph which had its disposition 

 to coagulation lessened. 



The learned Professor de Haen has taken notice of a curious 

 appearance of the blood, which he could not account for ; but 

 which, I presume, may be explained from some of the above 

 experiments. His observation is, " that having bled a person 

 in a fever, the blood was covered with an inflammatory crust, 

 and upon examining the crassamentum in one of the cups, he 

 found that it formed a sort of sac containing a clear fluid : 

 this fluid being let out, and the cup set by, on examining it 

 next morning, he observed a very firm crust covering the whole 

 again, and extending to the bottom of the cup." 1 I once met 

 with a case similar to this ; for, having bled a person into four 

 cups at ten o } clock in the morning, on looking at the blood 

 afterwards, at five in the afternoon, I found the serum had not 

 separated from the crassamentum in the first cup ; but the 

 crassamentum felt as if it contained a fluid in a bag, as Professor 

 de Haen has described it. Upon pressing it, the fluid gushed 

 out, and in a few minutes after being exposed to the air, coagu- 



1 Vide Rat. Medendi, cap. vi. 



4 



