100 The American Naturalist. [February, 
side the cell, which are the real units of the organism. They 
may not be recognizable morphologically, but they exist 
nevertheless as individual links in that chain of molecules of 
which we believe living protoplasm to be composed. As 
Quincke® has recently said “ bioiogical science must, well or 
ill, take into account the fact that the development of the cell 
and the life of organic nature depends on masses and layers 
which cannot be seen by the microscope alone.” Hence, the 
chemistry of the cell offers an interesting field of work full 
of promise, although for the most part it has been studied 
mainly with a view to obtaining more light regarding the 
general metabolic processes of the higher organisms. 
From a chemical standpoint, the living animal cell may be 
considered as a combination of varied chemical substances 
always in a state of unequilibrium, unstable in the highest 
degree, readily prone to break down by oxidation or cleavage 
into bodies of less complexity, each downward step in the pro- 
cess of disintegration, giving rise to the liberation of a certain 
amount of energy. These explosive, or it may be gradual, 
decompositions are going on continually as long as life endures, 
and chemical transformations and chemical decompositions 
are therefore an essential part of the life history of the cell, 
or of the organism of which it is an integral part. In them 
are hidden many of life’s mysteries, and some of the most in- 
tricate as well as important phases of physiological phenomena 
are closely connected with these more or less obscure chemical 
transformations. 
' This constant liberation of energy, so characteristic of the 
living animal cell, coming as it does from the continued dis- 
integration of the living substance of the organism creates 3 
demand for fresh material to supply the place of that which | 
has undergone this vital decay, otherwise the vital energies 
flag and the bodily structure withers away. The food material 
supplied to meet this demand, although it may be easily 
oxidizable or combustible cannot supply the needs of the or- 
ganism without becoming vitalized. As dead, inert matter it 
is simply combustible; it can exhibit energy as heat only like 
5Nature. Vol. 49. p- 6. 
