MRS. B.
The fact is, that heat is disengaged.[*] Whether any light be evolved, I cannot pretend to determine; but that heat is produced in considerable and very sensible quantities is certain, and this is the principal, if not the only source of ANIMAL HEAT.
EMILY.
How wonderful! that the very process which purifies and elaborates the blood, should afford an inexhaustible supply of internal heat?
MRS. B.
This is the theory of animal heat in its original simplicity, such nearly as it was first proposed by Black and Lavoisier. It was equally clear and ingenious; and was at first generally adopted. But it was objected, on second consideration, that if the whole of the animal heat was evolved in the lungs, it would necessarily be much less in the extremities of the body than immediately at its source; which is not found to be the case. This objection, however, which was by no means frivolous, is now satisfactorily removed by the following consideration:—Venous blood has been found by experiment to have less capacity for heat than arterial blood; whence it follows that the blood, in gradually passing from the arterial to the venous state, during the circulation, parts with a portion of caloric, by means of which heat is diffused through every part of the body.
EMILY.
More and more admirable!
CAROLINE.
The cause of animal heat was always a perfect mystery to me, and I am delighted with its explanation.—But pray, Mrs. B., can you tell me what is the reason of the increase of heat that takes place in a fever?