608 [June 11, 



It may be asked, How comes it that when the blood of a horse is 

 shed into a cup, the buffy layer coagulates as rapidly, or nearly so, 

 as the lower parts rich in corpuscles ? 



This is indeed a question well worthy of careful study. We know 

 that the liquor sanguinis left by the subsidence of the red corpuscles 

 within a healthy vein is incapable of coagulating when shed, except 

 in a slow manner, which is accounted for by the corpuscles that remain 

 behind in it. Hence it appears that when the blood as a whole is 

 shed into a glass, the agency of the ordinary solid leads the corpus- 

 cles to communicate to the liquor sanguinis, before they subside, a 

 material or at least an influence which confers upon it a disposition 

 to coagulate, though it still remains fluid for some time after they 

 have left it. Just as we have seen that a very short time of action 

 of the ordinary solid upon the blood as a whole is sufficient to give 

 rise to coagulation, so we now see that, provided an ordinary solid be 

 in operation, the presence of the corpuscles for but a little while is 

 enough to make the liquor sanguinis spontaneously coagulable, though 

 not immediately solidified. We shall see, before concluding, an illus- 

 tration of the importance of this fact to pathology. 



It remains to be added, that serous membranes resemble the lining 

 membrane of the blood-vessels in their relations to the blood, as is 

 implied by John Hunter's observation that blood, which had lain for 

 several days in a hydrocele, coagulated when let out. The same 

 thing is well illustrated in a frog prepared like this which I now 

 exhibit. About four hours ago, a knife having been passed between 

 the brain and cord to deprive the creature of voluntary motion in the 

 limbs and trunk, the peritoneal cavity was laid open in the middle 

 line, and its edges being kept raised and drawn aside by pins, I 

 seized the apex of the ventricle of the heart with forceps and re- 

 moved it with scissors. In a short time the whole of the animal's 

 blood was in the peritoneum, and it may be seen that it is still fluid 

 in spite of this long-continued exposure. When I first performed 

 the experiment three years and a half ago, the weather being cool 

 (about 45 Fahr.) and a piece of damp lint being kept suspended above 

 the frog to prevent evaporation and access of dust, I found that the 

 blood remained fluid in the peritoneal cavity for four days, except a 

 thin film on the surface, and a crust of clot on the wounded part of 

 the heart; but a piece of clean glass placed in the blood in the 



