PIONEER INVESTIGATIONS 
studied with great accuracy. The relations between the character and the 
amount of material burned in the body, the total amount of muscular work, 
and the efficiency of the human body as a machine are all of peculiar and 
special interest, and considerable emphasis will be laid upon them. 
PIONEER INVESTIGATIONS ON METABOLISM IN ITS RELATION 
TO MUSCULAR WORK AND ANIMAL HEAT. 
GASEOUS EXCHANGE DURING MUSCULAR WORK. 
It is outside the province of this report to enter into a detailed presen- 
tation of the experimental evidence which finally led to a knowledge of the 
source, the cause, and the mechanical equivalent of animal heat, and the de- 
velopment of the law of conservation of energy as applied to the human organ- 
ism. For the proper understanding of the problems subsequently treated in 
this report, however, it is necessary to outline certain of the fundamental re- 
searches, especially those bearing upon the relationships between the gaseous 
exchange, the output of mechanical work, and the mechanical efficiency of 
the human body. 
Prior to the time of Lavoisier, the conceptions of the physical and physi- 
ological processes as related to the chemistry of the human body were so 
devoid of scientific foundation that they can have now but little value except 
as an historic record of the trend of scientific thought at that time. With the 
advent of Lavoisier and his contemporaries, physiological and chemical research 
began to take a definite form which gradually led to the unfolding of natural 
laws and to the explanation of the phenomena of muscular action and of the 
transformations in the human body and their intimate relationships. 
Lavoisier's activity in studying respiration resulted in two remarkable 
memoirs by himself and Seguin, the first of which was published in 1789. a 
The results reported in this first memoir have particular significance in con- 
nection with the object of this book, in that Lavoisier recognized clearly the 
relationship between muscular activity and the gaseous metabolism, and not 
content with the simple determination of the carbon-dioxide excretion, actu- 
ally attempted the determination of the amount of oxygen consumed. 
The apparatus used in this research has been imperfectly described by 
Seguin, but his description tallies reasonably well with the two drawings at- 
tributed to Madame Lavoisier. 6 A careful study of these drawings shows us, 
in the most illuminating way, the attitude of Lavoisier and his contemporaries 
towards respiration experiments. One of the drawings illustrates an experi- 
ment in progress with the man resting, and the other the conditions obtaining 
in an experiment made during muscular work. Evidently a mask was used, 
which Seguin states was constructed of copper and held in place about the 
neck by wax or cement. Of particular significance is the fact that in both 
drawings we see, as evidently an essential part of the experiment, a physician 
■ Sgguin and Lavoisier, Memoires de I' Academic de3 Sciences, 1789. p. 566. Printed in Paris, 1793. 
« Two excellent drawings of Lavoisier's laboratory, both showing studies in the respiration of men, are given 
by Grimaux (Lavoisier, 1743-94, Paris, 1899, facing pages 119 and 129 respectively). Tigerstedt has 
reproduced one of these engravings showing the conduct of an experiment during rest (Tigerstedt's 
Handbuch der physiologischen Methodik, Leipsic, 1911, 1, p. 72). 
