'3b TlMEHRl. 
was again taken. The egested nitrogen now commenced 
to increase in quantity. 
Apart from any consideration of the relation of the 
amount of work actually done to the dynamical equiva- 
lent of the tissue supposed, according to LlEBIG'S view, 
to be consumed, these observations shewed, in a most 
pronounced manner, that the elimination of nitrogen 
depended upon the nitrogenous food consumed rather 
than upon the amount of work done. But when the 
amount of work done is taken into account and placed 
against the work-value of the tissue which, on Liebig'S 
hypothesis, would be represented by the amount of 
nitrogen eliminated, the results afford still more striking 
evidence of the fallacious character of Liebig'S theory. 
Shortly after the publication of the doctrine of the 
correlation of the natural forces, Joule, of Manchester, 
arrived at a definite expression for the relationship of 
" heat" and " work." This expression he termed the 
" mechanical equivalent of heat," and gave 1390 foot- 
pounds as the " work" corresponding to a unit of heat, 
or, in other words, that the work done in raising 1 lb. 
1390 feet, or 1390 lbs. 1 foot, would, if otherwise applied, 
produce sufficient heat to raise the temperature of one 
lb. of water one degree centigrade. 
In addition, Professor FRANKLIN by completely oxidis- 
ing albuminous matters (which form the basis of muscular 
tissue) has obtained an expression for the number of 
units of heat evolved in the process. The albuminous 
matters in the system, however, do not undergo complete 
oxidation ; a product resulting which is susceptible of 
further oxidation. Thus the number of the units of heat 
