PART I. 
INTRODUCTION. 
From the days of Count Rumford, who showed that the muscular work 
of two horses produced sufficient heat to boil water, until the present day, 
when mechanical efficiency and the study of body-movements in domestic 
and in manufacturing industries are receiving much attention, the muscular 
work of the human body, and particularly the efficiency of the body as a 
machine, have from time to time been experimentally considered. Unfor- 
tunately, most of the observations have been of a desultory nature, so that 
actual knowledge with regard to the extent and character of the chemical 
processes which are coincidental with muscular movements has but slowly 
accumulated. This is due primarily to the fact that in but few places are 
such studies possible. 
The practical results of studying body-motions and eliminating the ex- 
traneous muscular movements have been strikingly demonstrated on many 
occasions;" likewise, training has been shown to make possible prolonged and 
sustained effort by athletes; nevertheless these phenomena have either been 
considered as due in general to the better training — this broad term covering 
a multitude of operations — or the causes have been entirely disregarded, the 
majority of individuals being more interested in the practical results than 
in the causes. It is not, however, a matter of purely physiological interest, 
since with the present-day emphasis laid upon mechanical efficiency in the 
factory and in the home, it is a problem of much practical importance to know 
more exactly the mechanical efficiency of the human body and the best method 
of attaining the highest degree of efficiency. 
Our knowledge of training at this date is woefully deficient. Why a 
course of training should result in greater muscular strength, what changes 
in the body produce this end, and what is the best method to use for the 
purpose are at present either entirely unknown or our knowledge is based 
only upon practical experience. The trainer believes that a certain routine 
is best adapted to bring his athlete to the highest state of efficiency, and it 
would be a simple matter to follow this provided any number or even any 
two trainers agreed upon a particular routine. We have, however, on the 
one hand, the advocates of a high-protein diet and a meat diet, and on the 
other the advocates of a low-protein diet and a vegetarian diet, and it must 
be admitted that both have based their beliefs on arguments of great signifi- 
cance, although the asserted increased endurance of vegetarians rests as yet 
upon scant and fragmentary evidence. What is needed to place these prac- 
tical observations upon a scientific basis is a most careful study of the total 
metabolism, both nitrogenous and gaseous, combining with this, if possible, 
measurements of the muscular activity and the total energy transformations. 
« F. B. Gilbreth, Bricklaying system. New York, 1910. 
