388 
PHYSIOLOGY: ANDERSON AND LUSK 
kgm. (the original weight of the dog), it required 11.2 calories to move 
the dog 1000 meters. On the thirteenth day of fasting, the basal heat 
production having fallen to 14.2 calories, it required 10.6 calories to 
move the dog, now weighing 7.6 kgm., a distance of 1000 meters. 
A loss of body weight of 19% accomplished through fasting was 
accompanied by a fall in the basal metaboHsm of 28%, and an economy 
in the fuel necessary to move the body 1000 meters amounting to 15%. 
This method of calculation, however, does not give an accurate pic- 
ture of the interrelation between the nutritive condition of the dog and 
the amount of energy of metabolism necessary to accomplish a given 
amount of mechanical work, for it is obvious that to move a body 
weight of 9.2 kgm. through 1000 meters of distance would require a 
greater amount of energy than to move a body weight of 7.6 kgm. 
over the same distance. When the computation is based upon the 
energy equivalent in kilogr ammeters required to move 1 kgm. of body 
substance 1 meter through space, it is found that an average of 0.580 
kilogrammeter is required for that purpose with a maximum variation 
of =±=2.5% no matter what is the nutritive condition of the animal. (The 
reduction in this value after giving glucose in solution to the dog is 
dependent on the fact that the weight of the glucose solution (=±=280 
grams) was reckoned as part of the weight of the dog. The carrying 
of this inert mass, however, did not appreciably increase the level of 
metaboHsm, as has already been set forth above.) 
One may conclude, therefore, that the accomplishment of a given 
amount of mechanical work is always at the expense of a given amount of 
energy, and that the amount of energy required for mechanical work is 
independent of the physical condition of the subject and independent of 
the quantity of carbohydrate food present in the gastrointestinal tract. 
No experiments have been made after giving fat but, since the 
authorities (Zuntz, Atwater and Benedict) are agreed upon the equal 
economy of iso-dynamic values of these two classes of food substances 
in the production of a given amount of mechanical work, it may be 
assumed that ingested fat acts like carbohydrate in metaboHsm when 
work is performed. 
When meat is ingested the situation changes. Meat is a stimulant 
of the metabolism, as are several of its component amino-acids. Th,e 
effect of work upon the heat production during the fifth and sixth hours 
after giving 750 grams of meat, and during the third and fourth hours 
after giving 20 grams of alanin, is summarized in the following table: 
