9

ON ANIMAL HEAT. 279

simplicity, such as it Mas first proposed by Blackand Lavoisier . It is equally clear and ingenious ;and was at first generally adopted. Blit it was ob-jected, on second consideration, that if the whole ofthe animal heat was evolved in the lungs, it wouldnecessarily be much less in the extremities of thebody, than immediately at its source; which is notfound to be the case. This objection, however,which was by no means frivolous, is now satisfac-torily answered by means of the improved theoryof respiration which I mentioned last. Accordingto this hypothesis, you recollect, the changes whichthe blood undergoes in consequence of respiration,only begin in the lungs, and gradually continueduring circulation. Therefore the animal heat,w hich is the consequence of those changes, like-wise begins in the lungs, and afterwards continuesduring the whole circulation; and heat is thus uni-formly diffused throughout every part of the body.

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CAROLINE.

More and more admirable!

MRS. B.

Now let me hear whether you can explain howanimal heat is produced. You, Caroline, tell mein what manner it is first evolved in the lungs ?