OF THE BRAIN, ETC. 35 



constitution returns to its natural state, and the 

 secretions are restored. 



It has been observed, by a distinguished che- 

 mist, that " the experiments to determine the 

 specific heat of the blood are of so very delicate 

 a nature, that it is difficult to receive them with 

 perfect confidence." * The experiments of Dr. 

 Crawford for this purpose were necessarily made 

 on blood out of the body, and at rest. Now, 

 when blood is taken from the vessels, it imme- 

 diately undergoes a remarkable chemical change, 

 separating into a solid and a fluid part. This 

 separation is not complete for some time; but 

 whoever takes the pains to make observations on 

 the subject, can hardly doubt that it begins to 

 take place immediately on the blood being drawn. 

 Can experiments on the blood, under these cir- 

 cumstances, lead to any very satisfactory con- 

 clusions, respecting the specific heat of blood 

 circulating in the vessels of the body ? The 

 diluting the blood with large quantities of water, 

 as proposed by Dr. Crawford, does not altogether 

 remove the objection; for this only retards, it 

 does not prevent, coagulation; and some time 

 must, at any rate, elapse, while the blood is flow- 

 ing, and the quantity is being measured, during 

 which, the separation of its solid and fluid parts 

 will have begun to take place. 



More might be said on this subject ; but I feel 

 anxious to avoid, as much as possible, controver- 



* Thomson's History of the Royal Society, p. 129. 



D 2 



