THE STRUGGLE FOR LIFE. 211 
which is, the means by which the life of the individual cell 
is maintained, and how it is nourished. The exercise of 
any organ involves the expenditure of force, and as, in the 
machinery of the body, as in the machinery designed by 
man, force cannot be created, but only evoked and directed, 
it is certain that the performance of every action of the 
body and of every process of thought entails the destruction 
of pre-existing tissue, originally derived from a cell, since 
this is the only form in which force can be stored up in 
the body. If this is to be replaced, it can only be replaced 
by matter taken in from without, since ‘‘ex nihilo nihil fit,” 
out of nothing, nothing comes. I must therefore ask your 
indulgence while I say a few words on the Physiology of 
nutrition—a vast subject indeed, and one to which I can 
only allude in the briefest manner—and mention a few facts, 
in order that I may make myself intelligible to you, when 
I describe some of the ways in which Nature protects the 
body corporate from disease and death. 
To the question ; how is the necessary pabulum provided ? 
It seems at first sight a sufficient and self-evident answer 
to say ‘‘by the food taken into the body through the mouth.” 
This is in one sense true, but in another, absolutely untrue, 
because no food is ever directly taken into the body at all. 
Anatomically the stomach, together with the remainder of the 
alimentary canal, is nothing but a prolongation of the skin, 
and is completely continuous with it. If an animal be 
examined during its early development, this will be easily 
recognised, and not only so, but in some of the lower 
animals, such as the Sea Anemone, the skin and stomach 
may be made to change places, simply by turning the 
animal inside out, the former skin will then be found to 
act as an efficient stomach. In the higher animals, differ- 
entiation has proceeded so far that the glands with which 
the two organs are provided have acquired entirely different 
functions, and fulfil widely different purposes. The glands 
