652 THEORY OF COAGULATION. 



Hunter, that the ears of rabbits, the combs of 

 cocks, and the extremities of other animals, may 

 be rigidly frozen, and afterwards restored to life, 

 when gradually submitted to the influence of 

 warmth, it has been demonstrated by the expe- 

 riments of Hewson, Thackrah, Davy, Magendie, 

 and Prater, that the blood of animals may be re- 

 peatedly frozen, and afterwards coagulate when 

 thawed. Hence it is that hybernating animals, 

 including reptiles and other cold blooded species, 

 after being frozen for months, as in the higher 

 latitudes, are restored to activity by the returning 

 power of solar warmth. The influence of caloric 

 on the coagulating power of the blood is further 

 illustrated by the following observations of Dr. 

 John Davy, who found that the blood of a tro- 

 pical turtle, whose temperature was 91, coagu- 

 lated firmly in about two minutes : while that of 

 another turtle, whose temperature was 84.5, re- 

 quired five minutes to become solid ; and that of 

 another, whose temperature was 58, required 

 thirty minutes to coagulate firmly. (Anat. and 

 Physiological Researches, vol. ii. p. 10.) Mr. 

 Marshall also found that the blood of a tortoise 

 whose temperature was 55, that of the room 

 being 58, began to coagulate in eighteen mi- 

 nutes, and became solid in one hour and forty- 

 five minutes. But that when raised to the tem- 

 perature of 1 10, (falling to 80) it began in nine 

 minutes and a half, and was completed in twenty 



