140 On the Extrication of Caloric [Aug. 



Hunter concluded that in the coagulation of blood no heat was 

 given out. (Treatise on the Blood, &c. 4to. p. 27.) 



" A very different result, however, has since been obtained by 

 the author of a short article on the blood in Rees's Cyclopaedia. Ten 

 ounces of blood were drawn into a wooden bowl, in which a ther- 

 mometer was held. The temperature of the blood while flowing 

 from the vein was 93°. In six minutes the thermometer had sunk 

 to 89°, and coagulation commenced on the surface. On elevating 

 the bulb of the thermometer to the coagulum on the surface, the 

 mercury rose to 901°, and on again depressing it to the bottom of 

 the bowl it sunk to 89°. This was repeated twice, with nearly the 

 same result : and on the third trial the quicksilver rose to 91°. The 

 blood was now coagulated throughout ; and after this, the mercury 

 continued to descend regularly, and was no longer influenced by 

 changing the situation of the bulb of the thermometer. In this 

 experiment it clearly appeared that during the coagulation of the 

 blood caloric was extricated ; and in sufficient quantity, at one 

 time, to raise the thermometer 2°. 



" As it was desirable to confirm this result, and, of course, that 

 before obtained by Fourcroy, both so conformable to analogy, my 

 friend Mr. Ellis and myself, in presence of Professor Thomson, 

 performed the following experiment, in the month of April, 1810: 

 " Blood was received from the femoral artery of a dog, into a 

 small glass jar. The temperature of the blood flowing from the 

 artery was 99° Fahr.; and that of the apartment, during the expe- 

 riment, 46° Fahr. 



" One minute after the blood had been received into the vessel, 

 it began to coagulate, by a film on the surface. The bulb of a very 

 delicate centigrade thermometer was now placed into the blood at 

 the upper part of the vessel, and held there during a minute, with- 

 out touching the sides of the glass. It was then depressed to the 

 lower part of the vessel, where coagulation had not begun, and 

 held there in the same manner during the next minute. During 

 the next it was held at the top, and during the next at the bottom; 

 and so on, it was alternately elevated and depressed for 20 succes- 

 sive minutes after coagulation had begun on the surface. 



" When the bulb was first placed in the blood at the top, the 

 mercury gradually rose to 34° ; but when it was depressed towards 

 the bottom, it instantly fell to 30^-°. When again elevated, it rose 

 to 33^-° ; and when again depressed, sunk to 30°. A third time 

 brought to the surface, the mercury rose to 32° ; and a third time 

 depressed, it fell, in half a minute, to 28-^° At the next eleva- 

 tion the mercury rose to 31° ; and at the succeeding depression, fell 

 to 28-1°. At 18^ minutes after the blood had been drawn, when 

 the bulb of the thermometer was brought from the bottom towards 

 the top, the mercury rose from 24° to 25i°. It was now held at 

 the top for two minutes, and the mercury gradually fell to 24°. The 

 blood seemed now completely coagulated, and the experiment was 

 discontinued. 



