
CONSERVATION OF ENERGY IN LIVING ORGANISM. 12 lie 
of the materials oxidized. The natural inference is that prac- 
tically all the energy transformed in the body appears as heat 
and external work. ‘Two possibilities stand in the way of the 
acceptance of these results as a positive demonstration of the 
conservation of energy in these experiments and the natural 
corollary that it must obtain generally in the living organism. 
The first is that the measurements of energy may have been 
inaccurate. As regards this enough has been said to show the 
great improbability of any considerable error in the measure- 
ments of either income or outgo. ‘The other is that some form 
of kinetic energy concerned in the transformations may have 
escaped measurement. If there be such it must have belonged 
to the outgo. The question then is, was any form of kinetic 
energy other than heat and muscular work produced within 
the body and given off by it? 
Light and electrical energy are emitted by some of the lower 
animals, but it can hardly be assumed that any considerable 
amount of either is given off from the human body under 
ordinary conditions. It has been suggested that intellectual 
activity and nervous tension may be manifestations of some 
special forms of physical energy, the character of which is not 
yet understood. If such be the case any energy which is due 
to internal, mental, or nervous work must be transformed 
within the body, and unless there is some form of storage of 
which we have no conception it must be eliminated. It might 
be transformed into heat and leave the body in that form, as is 
the case with the energy of internal muscular work; it would 
then be measured with the other heat given off from the body. 
Or it might be eliminated in some other form unknown to us. 
In that case it must either pass through the copper wall of the 
respiration chamber without being changed to heat or it must 
have been changed to heat and measured, provided the quan- 
tity was large enough for measurement. In other words, the 
quantity must either have been extremely minute or it must 
be something the nature of which physical research has not 
revealed. 
The theory has been lately advanced that the body emits 
some form of energy in which rays of great wave length are 
concerned, and recent discoveries and conjectures regarding 
such forms of energy are of a kind to incite if not encourage 
9 
