ood or lymph stream undergo necrosis and
fail to give rise to secondary growths. Secondary growths present a
faithful reproduction of the structure of the primary tumour. Apart from
the lymph glands, the chief seats of secondary growths are the liver,
lungs, serous membranes, and bone marrow.

It is generally believed that the secondary growths in cancer that
develop at a distance from the primary tumour, those, for example, in
the medullary canal of the femur or in the diploe of the skull occurring
in advanced cases of cancer of the breast, are the result of
dissemination of cancer cells by way of the blood-stream and are to be
regarded as emboli. Sampson Handley disagrees with this view; he
believes that the dissemination is accomplished in a more subtle way,
namely, by the actual growth of cancer cells along the finer vessels of
the lymph plexuses that ramify in the deep fascia, a method of spread
which he calls _permeation_. It is maintained also that permeation
occurs as readily against the lymph stream as with it. He compares the
spread of cancer to that of an invisible annular ringworm. The growing
edge extends in a wider and wider circle, within which a healing process
may occur, so that the area of permeation is a ring, rather than a disc.
Healing occurs by a process of "peri-lymphatic fibrosis," but as the
natural process of healing may fail at isolated points, nodules of
cancer appear, which, although apparently separate from the primary
growth, have developed in continuity with it, peri-lymphatic fibrosis
having destroyed the cancer chain connecting the nodule with the primary
growth. This centrifugal spread of cancer is clearly seen in the
distribution of the subcutaneous secondary nodules so frequently met
with in the late stages of mammary cancer. The area within which the
secondary nodules occur is a circle of continually increasing diameter
with the primary growth in the centre.

In the rare cases in which the skin of the greater part of the body is
affected, the nodules rarely appear below the level of the deltoid or
the middle third of the thigh, the patient dying before the spread can
reach the distal portions of the limbs.

Handley argues against the embolic origin of the metastases in the bones
because of the rarity of these in the bones of the distal parts of the
limbs, because of the fact that secondary cancer of the femur nearly
always commences in the upper third of the shaft, which harmonise