A note on the healing in and migration of foreign bodies in the animal body

Abstract

We have made some observations on the difference in the behavior of different species of animals towards foreign bodies on which we wish to report very briefly.

If we apply very thin wires of copper around the neck of white rats in such a way that apparently they do not exert any marked pressure on the skin, these wires heal in at the ventral aspect of the neck, but not at the dorsal and lateral aspects, in a considerable number of cases, after they have at first produced some ulceration. About four weeks after the onset of the ulceration the skin begins to heal over the wire and soon the wire is buried deep in apparently normal tissue. Gradually the wire may migrate deeper into the tissues of the ventral parts of the neck and in one case it was found resting on the trachea, the tissues covering it being apparently quite normal. Thus the migration of foreign bodies can be imitated experimentally in certain cases.

In a large number of white nice and in three guinea pigs wires which had been applied in a similar manner, or even somewhat more tightly, did not heal in, but led to a transitory, more or less, superficial ulceration and scab formation, After some time such ulcers may heal, only to form again, in case the wire should continue to irritate the skin.

Microscopically we find in the rat in the first stage, that of ulceration, the base of the ulcer formed by fibrous or hyaline tissue which is infiltrated by fibroblasts. The wire is seen lying at the base of the ulcer surrounded by necrotic tissue and polynuclear leucocytes. On the whole, the capillaries run radially towards the surface of the ulcer, while the fibrous tissue and the fibroblasts are arranged in a direction more or less parallel to the surface of the ulcer. At the side of the ulcer near the tip of the regenerating epithelium, the growing connective tissue is more cellular and less fibrous and the capillaries are more dilated and a greater influx of polynuclear leucocytes is observed than at the base of the ulcer; at the latter place the pressure is greater and this may be responsible for the greater production of dense fibrous tissue and the poorer development of capillaries.