1883.] ! Organic Physics. 265 
of the cell contents, a quantity of free energy. The energy thus 
set free does not manifest itself as mass motion or as temperature. 
It is undoubtedly consumed in the formation of the starch mole- 
cules, and is one of the most important requisites to carbon 
assimilation. Thus, though the leaves possess the conditions 
which in animals result in motor activity, the energy set free by 
the oxidation of their protoplasm is but slightly thus employed, 
but is locked up in the starch product of assimilation. 
In the economy of plant life starch and sugar (its soluble form) 
are the contributions of the leaf to the growth of the tree. The 
: most important contribution of the root is ammonia, or some re- 
sultant nitrogen molecule. The result of the meeting of those two 
contributions we can but conjecture. There may be something 
analogous to animal nutrition, in which latter there is a degree of 
evidence that a nitrogen and a denitrogenized radical unite to 
form the albuminoid molecule. To this nutritive process ox- 
idation is constantly necessary. The formation ofthe protoplasm 
molecule cannot take place except motor energy is supplied, and 
this energy is furnished by oxidation of some constituent of the 
Sap current, 
A rapid résumé of a portion of the argument here developed is 
desirable. This is in relation to the successive periods of rest and 
activity which affect all animal life, and which have been re- 
cently traced in the life of each separate cell. Each cell has its 
active and its resting periods. During activity changes rapidly 
occur, and division takes place. This is always followed bya. 
period of quiescence; in which, perhaps, nutritive assimilation re- 
Places the active oxidation of the preceding period. We may 
"e trace more fully the true relations of the sleeping to the 
waking condition in animals. It is very probable that oxidation 
of organic substance never ceases within the animal body; but 
uS oxidation takes two distinct phases, which may be termed pri- 
_ ‘Mary and secondary oxidation, the former being the reduction of. 
Protoplasm, and requiring surface irritation, or its mental resultant, 
for its active operation; the latter being the reduction of hydro- 
carbons and other denitrogenized compounds, and acting under 
other conditions, 
Py is not used up in the body immediately upon its intro- 
‘ere is some storage process by which it is laid away 
“ntil required. It has been shown by the experiments of Petten- 
