encapsulated tumors of the interstitial or periglandular connective tissues.

Myxoma may occur in a diffuse form, causing a transformation of the gland into myxomatous material, or as circumscribed

tumors.

Myomata containing smooth muscle-fibers, and mixed tumors containing striated muscle-fibers, are rare.

Chondroma and osteoma have been observed.

Sarcoma is most frequently of the round-cell variety. It occurs in a diffuse form or as circumscribed nodules; association with fibroma and myxoma is not infrequent.

In diffuse sarcoma the gland undergoes a uniform enlargement, and the neoplasm extends rapidly, forming attachments to the skin and sometimes causing superficial ulceration. In other cases extension toward the chest-walls may occur, and may finally reach the pleura. On section through the gland a lobular character of the tumor may be recognized, and areas of fibrous or myxomatous character are visible here and there. Cystic conditions, sometimes met with, may be due to obstruction and consequent distention of the lactiferous tubules. The term cystosarcoma is appropriately applied to such cases. The sarcomatous tissue may project into the dilated tubules in a polypoid form (intracanalicular sarcoma), Section through the gland in such cases presents an appearance not unlike the surface of section of a head of cabbage. Cysts may also be formed in sarcomata by degenerative softening.

Localized sarcomata occur as nodular tumors arising from the connective tissue surrounding the acini. On section through the tumor the glandular acini may be seen within the nodules.

In any form of sarcoma the epithelium of the tubules and acini may undergo secondary proliferation, when the term adenosarcoma is applicable.

Adenoma of the mammary glands may be an independent growth, or may be associated with fibroma, sarcoma, or other tumors. The independent form presents itself as a circumscribed, encapsulated, nodular tumor, somewhat firmer than the substance of the normal gland. Microscopically it consists of more or less typical glandular acini. These are usually somewhat dilated, and the epithelial cells are larger than those of the normal gland (Fig. 64). Instead of a single layer of columnar cells, active hyperplasia may cause a complete filling of the acinus with epithelial cells. Fatty degeneration of the cells is not infrequent, and sometimes there is a certain amount of milk-secretion, causing additional distention of the cavities.

Carcinoma.-Carcinoma may develop from the tubules or from the acini of the glands. It may begin as an adenomatous tumor, which subsequently undergoes carcinomatous transformation, or may be a typical glandular cancer from the beginning.

In the cases primarily adenomatous the structure of the acini becomes atypical and the epithelial cells tend to penetrate the membrana propria and form irregular collections or columns in the interstitial tissue. Degenerative changes are often observed, among which fatty degeneration is most frequent. Mucoid degeneration and a form of caseation are sometimes met with, and calcification may take place in the interstitial tissues. Occasionally an attempt at formation of milk occurs in the cancer-acini. Varieties. Among the varieties of carcinoma are the medullary, the simple, the scirrhous, and the myxomatous.

Medullary carcinoma, or soft cancer, is characterized by its softness and the abundance of liquid (cancer-juice). It grows rapidly and soon invades a large part of the gland, and attaches

itself to the skin, which may finally be broken, exposing an ulcerated surface (Fig. 334). Actual inflammatory changes terminating in suppuration are not infrequent.

Scirrhous cancer is slower in growth, and is usually very hard; the skin is firmly attached to the tumor, and the nipple is usually retracted. On section the tumor is found to be of a firm, fibrous, and somewhat translucent character; extensions of the growth are seen radiating in various directions from the body of the tumor. Microscopically the growth consists of fasciculated connective tissue, enclosing round or elongated collections of cancer-cells (Fig. 72).

Simple carcinoma stands between the medullary and the scirrhous forms in point of hardness, as well as in point of malignancy. The three forms differ only in the relative amount of epithelial elements and fibrous tissue.

Myxomatous, colloid, or gelatinous cancer is a rare form in which the interstitial connective tissue suffers mucoid change, and the epithelial cells of the cancer-acini undergo more or less fatty or exceptionally mucoid degeneration (Fig. 73).

Results. Cancer of the breast may extend directly to the subcutaneous tissues and skin on the one hand, or to the walls of the chest and pleura on the other hand. Metastasis frequently takes place through the lymphatics, the axillary glands, as a rule, presenting the first evidence of metastasis. Malignancy varies with the softness or hardness of the tumors, the scirrhous form frequently having a comparatively benign character. Sometimes the increasing growth of connective tissue in this variety leads to practical cessation of the growth of the tumor.

Mammary cancers are much more frequent in the female than in the male sex. They are commonly met with after the age of forty, and traumatic influences seem to bear some relation to their

occurrence.

Cysts. Repeated reference has been made to the retentioncysts of the lactiferous tubules caused by compression or other forms of obstruction. The gland may contain a few or many cystic cavities about the size of a pea, containing whitish or milky liquid. Occasionally the contents of the cysts are cheesy (atheromatous). Distention of the acini of the glands in conse quence of obstructions to the outflow of milk may lead to large cystic tumors containing milk (galactocele). In the later stages the contents of such cysts may become thickened or caseous.

CHAPTER IX.

DISEASES OF THE BONES.

Anatomy and Development.-Bone is a dense form of connective tissue, the cement-substance being impregnated with lime-salts. It may be spongy or compact in character. On transverse section one sees certain oval openings, surrounded by concentric lamell of a substance containing lime-salts. Each opening is the end of a so-called Haversian canal, which with the surrounding lamella forms a Haversian system. The areas between the Haversian systems are filled with osseous tissue not arranged concentrically. Between the lamellæ of bony tissue are

In

seen irregularly oval spaces-lacunæ-from which run branching canaliculi. In preparations of fresh bone the lacunæ are found to be occupied by the bone-cells, which are irregular and have branching projections extending some distance into the canaliculi. the center of the bones are found hollow spaces containing the bone-marrow. This is a vascular tissue, in the meshes of which are found large and small rounded cells resembling the lymphoid cells, red corpuscles, ordinary leukocytes, and some nucleated red corpuscles. A form of cell of particular interest is the large multinucleated giant-cell, or myeloplaque. The marrow extends in the form of projections into the substance of the bone and communicates with the Haversian canals.

Surrounding the bone is the fibrous periosteum. This consists of a dense outer layer and a more cellular inner one, which is osteogenetic in function.

Development. The beginning of the change of the original cartilage into bone consists in the multiplication of the cartilage-cells and their arrangement in longitudinal rows. They grow into cartilage-corpuscles of considerable size, calcification at the same time occurring in the matrix between these cells. Simultaneously vascular projections extend inward from the perichondrium; the cartilage-cells and preliminary calcareous deposit are subsequently removed, primary marrow-spaces being thus formed. Bone-cells are deposited in the spaces between the original cartilaginous trabeculae, and at once begin to cover themselves with bony deposits, the cartilaginous trabeculæ gradually diminishing by absorption. By these processes a spongy form of bone is developed. Subsequently the concentric calcareous lamellæ of the Haversian systems are deposited within the spaces, and the spongy bone is thus converted into the dense form.

DISORDERS OF DEVELOPMENT.

Many congenital defects of development are observed, such as the appearance of supernumerary bones, the absence of certain bones, the failure of union between epiphyses and diaphyses, etc. These conditions are of little pathologic interest. The most important developmental disease is rickets.

RICKETS.

Definition.-Rickets or rachitis, is a constitutional disorder, attended with abnormal developmental processes in the bones, of which active proliferation of the cellular elements and lack of normal calcification are the most important.

Etiology. The causes of rickets are still very obscure. The disease is in some way connected with improper nourishment, though

there is probably also an inherited disposition. It has been sought to establish a connection between rickets and syphilis, but any such relation is doubtful. Various chemical theories have been offered in explanation. Formerly it was supposed that the presence in the digestive tract of lactic acid in excess prevented the proper absorp tion of calcium; this theory, however, is generally abandoned. The disease occurs in infants during the first year of life, and continues during the second and third years, after which the active manifestations subside.

Pathologic Anatomy.-Rickets leads to various deformities, principally situated in the long bones and skull. The epiphyses, as those of the wrist, ankle, etc., are swollen, and in more advanced stages the shafts of the long bones may be variously distorted.

Sharp bends (infractions) may be observed in the long bones, and complete fractures may occur. The alteration of the skull is characteristic. The head is large and square in shape, the forehead prominent, and the fontanelles remain open a long time. Osteophytes may form, and not rarely areas are found in the temporal or other bones in which the mineral substance is deficient or almost completely wanting (craniotabes), the spaces being filled by a parchment-like membrane. Deformities of the chest are frequent, the chicken-breasted condition being the most marked. In the beginning of the disease slight enlargement of the ends of the ribs at the junction with the costal cartilages, causing the

FIG. 335.-Rachitic enlargement of the end of a rib (modified from Bollinger).

beaded appearance called the "rachitic rosary," is observed (Fig. 335). Various distortions of the spinal column, flattening of the pelvis, and other deformities may be met with in marked cases.

The minute changes of rickets consist in a form of abnormal development, in which calcareous deposition does not progress in the normal manner, but is replaced by proliferation of the cellular elements. In consequence of this the bone presents irregular areas of partial calcification lying between portions made up of greatly proliferated and enlarged cartilage-cells. Projections from the marrow and periosteum extend deeply and visibly into the body of the bone, which is thus composed for the most part of osteoid instead of osseous tissue. The marrow-spaces are irregular and

excessive in size.

These changes in the bone are marked at