A suppurative change of this nature takes place in all heterologous new formations. The form of ulceration which is presented by cancer in its latest stages bears so great a resemblance to suppurative ulceration that the two things have long since been compared. The difference between suppuration and suppuration lies in the differing duration of the life of different cells. A cancer cell is capable of existing longer than a pus corpuscle, and a cancerous tumour may last for months yet still contain the whole of its elements intact. We are as yet able in the case of very few elements to state with absolute certainty the average length of their life. But among all pathological new formations with fluid intercellular substance there is not a single one which is able to preserve its existence for any length of time--not a single one whose elements can become permanent constituents of the body, or exist as long as the individual. The tumour as a whole may last; but its individual elements perish. If we examine a tumour after it has existed for perhaps a year, we usually find that the elements first formed no longer exist in the centre; but that in the centre they are disintegrating, dissolved by fatty changes. If a tumour be seated on a surface, it often presents in the centre of its most prominent part a navel-like depression, and the parts under this display a dense cicatrix which no longer bears the original character of the new formation. Heterologous new formations must be considered parasitical in their nature, since every one of their elements will withdraw matters from the body which might be used for better purposes, and since even its first development implies the destruction of its parent structures. In view of origin of new formations it were well to create a nomenclature showing their histological basis; but new names must not be introduced too suddenly, and it must be noted that there are certain tumours whose histological pedigree is still uncertain. _Printed in the United States of America_ FOOTNOTES: [1] Azure transparent spheres conceived by the ancients to surround the earth one within another, and to carry the heavenly bodies in their revolutions. [2] Book I., Prop. i. The areas which revolving bodies describe by radii drawn to an immovable centre of force do lie in the same immovable planes and are proportional to the times in which they are described. Prop. ii. Every body that moves in any curve line described in a plane and by a radius drawn to a point either immovable or moving forward with a uniform rectilinear motion describes about that point areas proportional to the times is urged by a centripetal force directed to that point.