18 PROPERTIES OF 



Next, to see the effects of air upon the blood, I tried as 

 follows : 



EXPERIMENT VI. 



Having laid bare the jugular vein of a living rabbit, I tied 

 it up in three places, and then opened it between two of the 



atmosphere. Fourcroy d stated that caloric contributes to the fluidity 

 of the blood, which becomes concrete in cooling. Gaubius 6 concluded 

 that the fluidity of the blood is preserved by the heat and motion of the 

 living body. Mr. Hewson's conclusions, that cold, so far from being 

 the cause of coagulation, actually retards it, and that it may be sus- 

 pended by freezing the blood and restored by thawing it, are now well 

 established. Senac f had noticed that the blood of fishes in winter 

 cannot be kept fluid by heat ; and Mr. Hunter g states that he observed, 

 offBelleisle, in 1761, the blood of a fish, at a temperature about 60, 

 immediately coagulate on being let out of the animal into the atmos- 

 phere at 70. Mr. Hey, h Mr. Thackrah, 1 Sir Charles Scudamore,J and 

 Dr. Davy, k all ascertained that a low temperature retards coagulation. 

 Thackrah found that human blood remains liquid upwards of sixteen mi- 

 nutes at 45, and freezes at a temperature between 20 and 30. Dr. 

 Davy has seen blood remain fluid for more than an hour at 32, and not 

 freezing until reduced some degrees lower; and he informs me that he has 

 seen the trout active in water in which ground-ice was forming at 32. As 

 mentioned in Note in, he infers that a heat of 120, which hastens the 

 coagulation of the blood, first makes it thinner and more liquid; and 

 he agrees with Mr. Hewson, that a low temperature, which retards 

 coagulation, renders the blood more viscid. 



Mr. Hunter 1 froze some blood rapidly by subjecting it to a cold 

 below zero ; after thawing the blood, it became fluid, and then coagulated, 

 he believed as quickly as if it had not been frozen. He found that 

 portions of muscle removed instantly from a live frog, and from a 

 bullock just knocked down, contracted after having been frozen and 

 thawed in the same manner, though irritation did not produce any 

 sensible motion in the fibres. "This," he says, "is exactly similar to 

 the freezing of blood too fast for its coagulation, which, when thawed, 

 does afterwards coagulate, as it depends in each on the life of the part 

 not being destroyed." And he observed that a high temperature acts 

 alike as an excitement to the coagulation of blood and to the contraction 

 of muscle, " both apparently depending on the same principle, namely, 

 life." Although Hunter never saw the life of a whole animal, which 

 had been frozen, return by thawing, Dr. Davy m has shown that the 



d Journal de Physique, 4to, Paris, 1749, h Obs. on the Blood, 8vo,Lond. 1779, p.34. 



torn, xliv, p. 382. * On the Blood, ed. 1834, p. 67. 



e Institutiones Pathologise, 336, 8vo, J Essay on the Blood, p. 21. 



Leid. Batav. 1758. k Researches, ii, 75. 



f Traite du Cceur, ii, 133, ed. 1749. 1 Works, ed. by Palmer, iii, pp. 109-13. 



* Works, ed. by Palmer, iii, 26. Researches, vol. 2, p. 121. 



