ANIMAL HEAT. 24-1 



ally.P Man and other non-hybernating animals breathe more 

 quickly when exposed to cold (no doubt for the purpose of sup- 

 plying heat) till the powers become exhausted. 9 



The higher the temperature of the animal, the more extensive 

 is the aggregate surface of the air-cells, the more blood passes 

 through its lungs, and the more necessary to its existence is 

 respiration. The lungs of cold-blooded animals are not sub- 

 divided into minute cells, but formed into vesicles ; and birds, 

 which have the highest temperature among animals, are drowned 

 the soonest. r Respiration is much slower in the cold-blooded. 

 Dr. Stevens found an alligator breathe but three or four times 

 in a minute, though young, and agitated at being held. 8 



The changes of the air by the blood are seen to be effected 

 entirely by the red particles. Prevost and Dumas found that the 

 number of red particles is proportionate to the temperature. 



If the blood circulates without being first properly changed in 

 the lungs, the temperature is below the natural standard. Those 

 who have the blue disease (cceruleans l ), some of whose blood 

 reaches the left side of the heart without passing through the 

 lungs, are cold : and coldness is a symptom of hydrothorax, and 

 of the repletion of the air-cells with mucus in chronic bronchitis; 

 in the former of which affections the lungs cannot fully expand; 

 and in the latter the air is prevented from coming fully in contact 

 with the air-cells, and mucus Priestley found to be a barrier to 

 the influence of oxygen on the blood, (p. 14-9.) 



In cold climates, and in temperate ones in cold weather, animal 

 food is desired and taken in abundance ; in hot climates, and 

 during the summer in temperate regions, light vegetable food is 

 preferred, and the appetite is less. We may conceive the former 

 diet more calculated to support a process similar to combustion, 

 and under the former circumstances we have seen that the 

 changes of the air in the lungs are actually more considerable. 



P Dr. Edwards, 1. c. p. 306. sq. <M. c. p. 301. 



r Boyle's Works, vol. iii. p. 368. s 1. c. p. 35. 



r " Sometimes the septa of the heart are imperfect, sometimes the aorta arises 

 with the pulmonary artery from the right ventricle, as in the tortoise. In such 

 instances, the chemical changes can take place in the lungs but imperfectly. 



Consult a host of cases in J. C. Hem's Diss. de istis Cordis deformationibus qua 

 sanguinem venosum cum arterioso miscere permittunt. Gottirig. 1816. 4to." 



Mr. Allan Burns, Essay on Diseases of the Heart, and Dr. Farre, Treatise on 

 Malformation of the Heart, give accounts of these cases. See also Andral. 



it S 



