What is true of the cells is also true of organs composed of them. Each organ can be regarded as a distinct animal (a parasite is preferable for comparison) which has its own nervous system (the ganglia), but is fed and controlled by the organism as a whole. Degeneration of this organ may therefore be an expression of a local state peculiar to it and either beneficial or maleficent, or both in inverse degree, to the organism as a whole, or it may be the expression of a general defect in the whole organism. The sclerotic states of the appendix vermiformis in man and of the human liver are, as Kiernan has shown, two excellent illustrations of the degeneracies last described. Man, in common with the four anthropoid apes, has a little thin tube attached to the cæcum known as the appendix vermiformis. In the early embryo it is equal in calibre to the other bowels, but ceases to grow proportionately after a certain time. In the new-born child it is almost as large as in the adult. As this tube proved disadvantageous to man's precursor (as it does to certain mammals) from catching foreign bodies which form the nucleus of enteroliths or bowel stones, it has lost the nutritive supply of the other intestines and is tending to disappear. It is often absent in man. The defect in its structure, while predisposing to the attacks of germs and an expression of its own degeneracy, is an evidence of an advance in evolution in the organism as a whole by which great danger and waste of nutritive force are avoided.