414 NUTRITION. 



The elevation in temperature that attends muscular 

 action is produced directly in the substance of the muscle. 

 This important fact was settled by the very interesting and 

 ingenious experiments of Becquerel and Breschet. Intro- 

 ducing a thermo-electric needle into the biceps of a man 

 who used the arm in sawing wood for five minutes, these 

 physiologists noted an elevation of temperature of one de- 

 gree centigrade J (nearly two degrees Fahr.). The produc- 

 tion of heat in the muscular tissue was even more strikingly 

 illustrated by Matteucci, in experiments with portions of 

 muscle from the frog. Not only did he observe absorption 

 of oxygen and exhalation of carbonic acid and water after 

 the muscle had been removed from the body of the animal, 

 but he noted an elevation in temperature of about one de- 

 gree Fahr., following contractions artificially excited. 3 



It is useless to multiply citations of experiments illus- 

 trating the facts above noted, or to discuss elaborately the 

 theoretical transformation of a given quantity of caloric into 

 a definite and invariable amount of work. The conditions 

 in the animal economy are such that we cannot exactly ap- 

 preciate the loss of heat by the cutaneous and respiratory 

 surfaces ; nor can we follow the processes in the body which 

 involve the disappearance of oxygen and the evolution of 

 carbonic acid ; the exact changes undergone by the hydro- 

 carbonaceous elements of food and constituents of the body ; 

 the amount of heat involved in the changes of the nitro- 

 genized elements ; and, in short, we cannot make the correc- 

 tions that are absolutely necessary before we can hope to re- 

 duce the question of the oxidation of certain principles in the 

 body, the development of heat, and the generation of mechan- 

 ical force, to exact mathematical calculation. This has been 

 attempted by Beclard 3 and others, who have endeavored to 



1 BECQUEREL ET BRESCHET, Premier memoire sur la chaleur animale. Annales 

 de chimie et de physique, Paris, 1835, tome lix., p. 113. 



2 MATTEUCCI, Recherches sur les phenomenes physiques et chimiques de la con- 

 traction musculaire. Comptes rendus, Paris, 1856, tome xlii., p. 651. 



3 BECLARD, DC la contraction musculaire dans ses rapports avec la temperature 



