8 MUSCULAR WORK 
by a pure-blooded Arabian horse which, in the state of repose, exhaled 852.42 
grams of carbon dioxide per hour. He states that the intensity of the respira- 
tion of this horse was remarkable. Lassaigne's technique was obviously faulty. 
HEAT OUTPUT OF THE ANIMAL BODY. 
The earliest attempts to measure the heat given off from the body of a 
living animal were those made simultaneously by Adair Crawford ° in Glasgow 
and Lavoisier and de la Place b in Paris. Crawford, with a water calorimeter, 
measured the heat given off from a guinea-pig and likewise made an estima- 
tion of the amount of carbon dioxide produced. Lavoisier and de la Place, 
using the melting of ice for the measure of the heat production, placed in 
their calorimeter a guinea-pig and weighed the water resulting from the melt- 
ing of ice; subsequently they placed the guinea-pig under a bell-jar and 
determined the amount of carbon dioxide produced. Having tested their cal- 
orimeters by burning a wax candle or some pure carbon, both Lavoisier and 
de la Place on the one hand and Crawford on the other attempted to compute 
the amount of heat that would be required to produce the given amount of 
carbon dioxide. The results of their computations showed a fairly satisfactory 
agreement, indicating that the combustion was proportional to the amount 
of carbon dioxide produced. The interpretation of results is particularly 
interesting in showing that Crawford still adhered to the phlogiston theory, 
his explanation of the phenomena being determined chiefly by his experience 
with specific heats. According to his belief, the heat given off by the body is 
absolute heat which is abstracted from the pure air in its passage through the 
lungs, or, to quote him exactly: 
That animal heat depends upon the separation of elementary fire from the air in the 
lungs is moreover supported by the experiments which have been brought in proof of the 
third and fourth propositions. 
In summing up his opinion, he says: 
Hence it clearly follows, that, in the respiration of animals, as well as in the com- 
bustion of wax, oil, and tallow, the pure air is altered in its properties by its combination 
with the inflammable principle; and since we know that the union of these elements is 
universally accompanied with the extrication of heat, and particularly that, by this union, 
a large quantity of elementary fire is disengaged from the air in the combustion of oleagi- 
nous substances, we may conclude that, in the process of respiration, a similar extrication 
of fire takes placed .... 
Since, therefore, it has been proved that elementary fire is absorbed from the air in 
the process of respiration, and since the quantity that is thus absorbed is not only adequate 
to the effect which we have been endeavoring to explain, but also proportional to it, we 
may safely conclude that it is the true cause of animal heat. e 
Crawford distinctly states: 
I do not mean to assert that elementary fire is really capable of being chemically com- 
bined with bodies . . . Before this can be admitted it must be proved that heat is a sub- 
stance; and I do not know that any experiments have hitherto been published which 
demonstrate the materiality of that principle/ 
a Crawford, Experiments and observations on animal heat, 2d ed., 1788, J. Johnson, London. According 
to the preface of this book the experiments were made at Glasgow during the summer of 1777 and were 
presented to the Royal Medical Society during the winter of 1778. They were first published in 1779 
(J. Murray, London, 1779). 
6 Lavoisier and de la Place, M6moires de l'Acaddmie, 1780, p. 355. See also Lavoisier, Traits' 616mentaire de 
Chimie, Paris, 1801, p. 1. The irregularity incidental to the dating of publications issued between 
1700 and 1880 has been the subject of comment by J. Rosenthal in a German translation of the two 
articles by Lavoisier and de la Place (Zwei Abhandlungen fiber die Warme von A. L. Lavoisier und P. S. 
de la Place, 1780 u. 1784. Ostwald's Klassiker der exakten Wissenschaften, No. 40, Leipsic. 1892). 
c Crawford, loc. cit., p. 358. <* Ibid., p. 359. « Ibid., p. 361. / Ibid., p. 363. 
