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DIETARY STUDIES OF A WALKING TRIP. IOI 
and of 4.75 pounds for H. L. K. For the remainder of the 
study there was a gain of 1.5 pounds with C. H. C. ora net 
loss of 7.5 pounds for the whole period, and no further change 
in the case of H. L. K. To be sure, it is well known that 
body weight alone is by no means a reliable indicator of actual 
body conditions. Loss in weight may be of little significance 
if due to increased elimination of water, and an apparent gain 
may be a real loss, as in the replacement of fat by water. The 
loss of weight at the start is not surprising since the suddenly 
increased muscular exertion would naturally draw upon the 
reserve materials for the body for a time regardless of the diet. 
At the same time, so large a loss tends to confirm the belief 
that the diet was not large enough. A study of the menus 
shows that more food was eaten on the last days of the trip. 
This also would indicate that the body has been insufficiently 
supplied. Further evidence is found in the fact, mentioned 
beyond, that both subjects recovered normal weight in a few 
days after the trip had ended. 
As no means were available for estimating the outgo of nitro- 
gen, no determination of the gain or loss of this element was 
possible, but there is further evidence that in the case of H. L. 
K. the amount of energy supplied was insufficient. A few 
months before, several experiments had been made with this 
subject in which it was shown by means of the respiration calo- 
rimeter that his normal heat production, while sitting as quietly 
as possible, was about 90 calories per hour. Long series of 
similar experiments with other subjects show that the heat 
elimination during sleep was at least 50 calories per hour. 
Assuming that nine hours were spent in sleep the heat produc- 
tion per day of this subject when at rest becomes 9 X 50+ 15 
X 90 = 450 + 1350= 1800 calories. 
Using Haughton’s* formulas for the work done in walking 
both on horizontal and inclined planes, a rough estimate, which 
however, is a minimum figure, of 963,225 foot pounds per day 
may be obtained. ‘This divided by 3,088, the mechanical equiv- 
alent of 1 calorie, gives as the consequent heat production, 312 
calories, making a minimum of 2,112 calories actually required 
as compared with 1,866 furnished by the food. 

* Principles of Animal Mechanics, pp. 57, 58. 
