are frequently found in connection with femoral and inguinal herniæ. Roser believed that lipoma in subperitoneal spaces usually occupied by hernia is a frequent cause of hernia. A subperitoneal tumor of the anterior abdominal wall sometimes, by displacing the abdominal muscles, becomes subcutaneous, especially near the umbilicus. If the tumor is situated between the folds of the broad ligament, it simulates very closely an ovarian tumor. The removal of omental lipoma has proved more successful than the removal of tumors from behind the peritoneum of the posterior abdominal wall. Meredith removed

bifida in a child eight months old (after Témoin).

successfully an omental lipoma weighing fifteen and a half pounds. Förster saw one that weighed fiftythree pounds. Waldeyer described a lipo-myxoma of the mesentery that weighed sixty-three pounds.

Subserous lipoma of the colon is met with occasionally. The appendices epiploicæ are often the seat of polypoid lipomata. Lipoma of the abdominal organs and of the subperitoneal layer of fat are not recognized before the abdomen is opened. If abdominal section reveals the existence of a lipoma in the retroperitoneal space, its removal should not be attempted if, as is so often the case, it dips down deeply on the side of the vertebral column, unless the tumor interferes with an important function or is the cause.

FIG. 285.-Meningeal lipoma simulating a spina of pain. If the tumor is more favorably located, the peritoneum covering it should be incised over the most prominent part of the tumor, and the tumor should be removed by enucleation. After the tumor is removed the peritoneal incision should be sutured.

Submucous Lipoma.-Submucous lipoma of the gastro-intestinal canal is rare. Virchow examined a submucous lipoma of the stomach as large as a walnut. Turner has seen a fatty tumor, the size of a large walnut, growing in the submucous tissue of the large intestine and projecting into the lumen of the bowel near the ileo-cecal valve. Submucous intestinal lipomata may cause intussusception, and thus become

a source of danger to life. A few instances of submucous lipoma of the larynx have also been reported.

Meninges of the Brain and Spinal Cord.-Lipoma of the meninges of the brain and spinal cord is a heterotopic tumor which develops from a displaced matrix of lipoblasts. Tauber records a case where the tumor was located in the tubercula quadrigemina on the right side, and had given rise to destruction of brain-tissue from pressure. Rokitansky has seen cases of lipoma upon the internal surface of the dura mater and in the lateral ventricle. Polypoid masses of fat are occasionally associated with protrusions of the spinal or cerebral meninges, and fatty tumors may be found as a pathological curiosity in the central nervous system. Chiari found two lipomata the size of a pea under the arachnoid, and Weichselbaum found one in the posterior lobe of the hypophysis in a soldier twenty-two years old. Lipomata are frequently observed at the seat of a spina bifida occulta, which may even penetrate inside the theca (Fig. 285).

In the cases of meningeal tumors examined by Recklinghausen and Obre the tumors contained striped muscular fibres, showing that the matrices were composed of displaced fetal tissue. A lipoma complicating a spina bifida greatly complicates the diagnosis. The presence of a solid tumor over the spine in children should induce the surgeon to look for, and to be prepared to treat, a spina bifida at its

base.

Intermuscular Lipoma.-Fatty tumors in rare instances have been found between nearly all the great muscles, and have given rise to great difficulty in diagnosis. Myxo-lipoma, according to Lücke, occurs most frequently below the gluteal fold, between the muscles of the thigh, and frequently penetrates the ischiatic foramen.

Intermuscular lipoma being more liable than superficial tumors to undergo transition into sarcoma, their operative removal is rendered so much more imperative.

Periosteum. As a heterotopic tumor lipoma of the periosteum must be mentioned. Sutton collected nine such cases representing so many different bones. The heterotopic nature of periosteal lipomata has been established by microscopical examination, which in each. specimen showed traces of striated muscle-fibre. Without an exploratory incision or an examination of tissue removed it would be next to impossible to make a positive diagnosis.

Joints. Subserous lipoma of joints, from the location of the tumor, appears as a diffuse growth. The lobes of the branching tumor present a racemose or arborescent appearance; hence these tumors are known and described as lipoma arborescens. So far, 16 cases of lipoma of the

knee-joint have been recorded. In this joint Schmolk describes two varieties: (1) the diffuse and (2) the circumscribed. The diffuse variety is not a tumor, but an inflammatory swelling of a tubercular nature with fatty degeneration of the synovial villi. The circumscribed form has, according to König, its starting-point in the retrosynovial fat-tissue in the same manner as the retroperitoneal lipoma. The tumor projects into the joint through a rent in the synovial membrane caused by an injury or otherwise. Subsynovial lipoma is found most frequently in the knee-joint, but has also been seen in the shoulder-joint. The fringes of the tumor are covered by the synovial membrane. If the tumor disturbs the function of the knee-joint, its removal by arthrectomy is indicated. Thorough removal under strict aseptic precautions is not followed by recurrence and yields a satisfactory functional result. Tendon-sheaths.-Lipoma outside the tendon-sheaths has been described by Ranke and Trélat. It is found most frequently along the tendon-sheaths of the flexor tendons of the hand. Lipoma inside the tendon-sheaths springs from the adipose tissue of the mesotendon. It develops usually as a multiple tumor which presents an arborescent appearance, and it is easily mistaken for tuberculosis of the tendonsheaths and for plexiform neuroma. According to Hammann, Sprengel, and Haeckel, it can be treated successfully by excision.

Eye. Subconjunctival lipoma is a rare affection of the eye. It occurs most frequently near the point where the conjunctiva is reflected from the lower lid to the eyeball, and it is almost confined to children. As a rare retrobulbar benign tumor a lipoma is found in the cushion of fat behind the eyeball, producing, according to its size, more or less displacement of the eyeball.

Broad Ligament.-Lipoma of the broad ligament as a subserous tumor is very rare.. Pozzi saw a case of this kind in which the tumor was mistaken for an ovarian tumor because of the misleading sense of fluctuation. The patient suddenly died of embolism three days after an exploratory incision.

Vulva.-Lipoma of the vulva arises in the fatty tissue of the mons veneris, and often reaches large dimensions. Stiegele operated on one which weighed ten pounds. In one of Bruntzel's cases the tumor increased greatly in size during pregnancy.

Scrotum.-Lipoma of the scrotum occurs rarely as a subcutaneous tumor. Fatty tumors of the cord often reach considerable size. Park successfully removed a large lipoma of the cord, and he refers to a number of similar cases. Sarazin has collected from different sources 26 cases of lipoma of the spermatic cord.

XIX. MYXOMA.

THE frequent occurrence of myxomatous degeneration of the stroma of benign and malignant tumors and the rarity with which pure myxomatous tumors are found have induced some authors to abandon myxoma as a separate class of tumors and to include it among the fibromata. Myxoma is a tumor which presents so many characteristic peculiarities that it is well to give it a separate place in the classification of tumors, and not to regard it as a variety of oedematous degeneration of other connective-tissue type of tumors.

Definition. A myxoma is a tumor composed of mucous tissue resembling Wharton's jelly in the umbilical cord. Virchow selected Wharton's jelly of the umbilical cord as a prototype

of the tissue of which a myxoma is composed (Fig. 286).

FIG. 286.-Connective-tissue cells from young umbilical cord: processes of cells

fibrous elements slightly developed (after Piersol).

In the embryo the connective tissue is identical in structure with Wharton's jelly. The meshes of the cellular network are occupied by a semi-gelatinous, indifferent, and but slightly differentiated intercellular substance containing few fibres and occasional wandering cells. During the devel- unite to form protoplasmic network; opment of myxomatous into connective tissue the fibrous tissue in the meshes becomes more abundant, while the intercellular substance is diminished in quantity. If a group of cells should become arrested in their development at an early stage and be set aside, it is to be expected that tissue-proliferation from them would result in a connective-tissue tumor of lowly-organized tissue-a myxoma. On the contrary, arrest of development at a later stage would result in a tumor-matrix which would produce a connective-tissue tumor of a higher type-a fibroma. The stage at which development of the mucous cells in the embryo is arrested determines whether the tumor from such a matrix is to be a myxoma or a fibroma. The intrinsic capacity of mature connective tissue to revert to its original embryonic state accounts for the frequency with which the stroma of all tumors undergoes myxomatous degeneration. A post-natal

matrix of myxoma is created if the pre-existing connective-tissue cells revert to their original embryonic state and remain unspecialized.

Histology. The histological structure of a myxoma is subject to many variations. The variable structure depends on the amount and character of the intercellular gelatinous substance and the abundance and vascularity of its stroma. Mucin is a substance which in the living body is rapidly destroyed and eliminated. In a myxoma the retention of this substance gives rise to hydropic conditions, and this retention occurs in myxomatous tumors if the production and absorption of mucin are arrested.

Myxoma may occur as a clear, colorless, gelatinous mass which differs from fluid only in its greater consistence. The delicate stroma of such a jelly-like mass contains small blood-vessels which nourish the lowly-organized tumor-tissue. Such tumors are found in the antrum of Highmore. In the firmer variety the translucency is lessened by a more copious stroma and by larger blood-vessels. The prognosis in the latter form is less favorable than in the former, on account of the more active cell-proliferation. The capsule of a myxoma is composed of connective tissue which has become condensed by pressure on the part of the tumor-tissue.

The typical myxoma is composed of a network of branching cells, the intercellular substance in its meshes being composed of a gelatinous homogeneous substance which contains mucin. The nuclei of the cells are large. If the cells of the tumor

are few and the stroma is in an extremely hydropic condition, the tumor is called a hyaline myxoma (Fig. 287, A). If the cells are more abundant and less stellate, it is called a medullary myxoma (Fig. 287, B). If the tumor is very vascular, we speak of a myxoangioma. Klebs found that myxomatous degeneration takes place in cells which are in close proximity to blood-vessels, and that it appears first as a vacuole in the protoplasm of the cell. As a component part of other tumors, benign as well as malignant, myxomatous tissue is very common, in which case the nomenclature of the tumor is modified by substituting a compound word for the single word and retaining the name of the primary tumor, as adeno-myxoma, chondro-myxoma,

FIG. 287.-Myxoma: transition of (A) hyaline form into (B) medullary form; X 250 (after Perls).