from the vessel walls. The round cells which are found interspersed between the keloid tissue Thorn is inclined to believe are the product of an inflammatory process near the surface of the tumor. The new tissue is unquestionably derived from the pre-existing connective tissue of the corium under the influence of an as yet unknown cause. The appearance of blood-vessels and the arrangement of fibers around them are well shown in Fig. 266. While keloid is an obstinate affection to all kinds of local treatment, it differs from sarcoma in that it remains limited to the tissues primarily affected and never gives rise to metastasis. After having attained a certain size it often remains stationary for an indefinite time. That such a tumor should occasionally undergo transformation into a sarcoma is not surprising considering the imperfect development of the tissues of which it is composed.

Scar Keloid.-Another variety of fibroma in the skin is the fibrous tumor which starts in scar-tissue following a wound, the healing of a

burn, or other surface lesions, particularly tubercular ulcers. Alibert in 1814 was the first to describe this fibrous tumor, and from its resemblance to carcinoma he called it "keloid." Keloid resembles clinically some of the granulomata, and under the microscope it is a compromise between a fibroma and a sarcoma. Its frequent occurrence in tubercular scars and

in minute scars resulting from small punctured wounds has led the writer to suspect that it might represent a particular form of tubercular inflammation. We are, however, not in a position to prove its tubercular origin and nature, and its clinical behavior would certainly tend to negative the idea that it is a form of sarcoma. For the present we must include it among the fibromata, although strongly inclined to believe that before long it will have to be classified with the infective swellings. The colored race is peculiarly predisposed to keloid. The sting of an insect, the prick of a needle, or a small abrasion frequently acts as the exciting cause. The wearing of ear-rings is also a frequent

cause.

The patient whose photograph is shown in Fig. 267 was the subject at the same time of numerous keloids of the skin of the chest and of the back.

Keloid sometimes affects different parts of the body at the same time, but always develops in a scar, which may be so small as to elude detection (Fig. 268). The tumor slowly increases in size up to a certain point, and after having remained stationary for from ten to twenty years may slowly disappear -one of the strongest proofs that it is not a true tumor. The keloid tissue is characterized by its great vascularity as compared with other fibromatous tumors and by the existence of numerous connective-tissue spaces lined with endothelial cells. The inflammatory part of a keloid is shown by the numerous leucocytes in the perivascular spaces. From the structure of a keloid it would be reasonable to assume that occasionally it is transformed into a sarcoma. The benign clinical aspects of a keloid render it easy to distinguish between it and a malignant tumor of the scar-tissue.

The treatment of keloid is extremely unsatisfactory. External applications and compression are useless. Recurrence even after thorough extirpation is common. The only treatment is by thorough excision. The incisions should include a zone of apparently healthy tissue at least a few lines in width. The scar following the operation should be protected carefully for a long time.

Mucous Surfaces.-Fibroma of the mucous surfaces resembles that of the skin in every respect except that the surface of the tumor

is covered by mucous membrane instead of by skin, and that the tumor in this locality is more prone to oedema. Many of the polypoid growths in mucous channels are oedematous fibromata. If pendulous, they should be removed with the wire écraseur; if sessile, by excision or by enucleation.

Subcutaneous Connective Tissue.-Two kinds of fibroma, clinically distinct, are met with in the subcutaneous connective tissue-the painful tubercle and the soft multiple fibroma of Recklinghausen.

Painful Subcutaneous Tubercle.-This is a little hard tumor, not larger than a pea, noted for its painfulness, in the subcutaneous tissue. This tumor was first described by A. Petit, Cheselden, and Camper. The best description was given in 1812 by Mr. Wm. Wood. These tubercles are most frequent in the extremities, especially the lower. They are more frequent in women than in men, they rarely occur before adult life, and they are seldom multiple. Examined under the microscope, they are seen to be composed of dense fibrous tissue, with filaments laid inseparably close together in the fasciculi and compactly interwoven. The young cells in the periphery of the tumor contain large nuclei. The pain and tenderness appear either contemporaneously with the tumor or after the tumor has reached a certain size. The pain, which is usually paroxysmal, but which can always be provoked by pressure, is sometimes attended by muscular spasms. Velpeau regarded these tumors as neuromata. Dupuytren, who made several very careful dissections, was never able to trace their connection with nerve-fibres. Other surgeons have succeeded in finding the nervefilaments with which these tumors are connected. In one case the writer could trace the nerve from the capsule of the tumor on both sides. The nerve was no larger than a fine silk ligature. There can be no doubt that these tumors are connected with sensitive nerve-filaments. Their removal by excision is often followed by recurrence. Successful removals of recurrent painful tubercles are reported by Sir James Paget and by Mr. Lawson Tait.

Multiple Subcutaneous Fibroma.-The true pathology of multiple fibrous tumors of the subcutaneous tissue was pointed out in 1882 by Recklinghausen. He ascertained that these tumors are invariably connected with the sheaths of terminal nerves. They are sometimes congenital, but they usually develop after puberty. In number they vary from a few to more than a thousand. In the case of Michael Lawler, described in Smith's monograph, they were estimated at least at two thousand. This affection was formerly known as "molluscum fibrosum" (Pl. 8, Fig. 2). In size these tumors vary from that of a hemp-seed to that of a filbert. In the course of time some of the

1. Keloid of external ear (after Klebs): a, dense fibrous cutis tissue with wide juice-canals, endothelial lining, and hyaline ground substance; /, fibrillated connective tissue with abundance of cells, with large vessels, perivascular proliferation, and at different places wide juice-canals; c, attenuated epidermis, the papillæ having in part disappeared. (Obj. 5, oc. 3.) 2. Multiple subcutaneous fibromata.