Malassez has made careful researches concerning the origin of cysts of the jaws, which have led him to the conclusion that they start from what he calls "débris paradentaires épithéliaux," which he was able to demonstrate in embryos as well as in the adult. Such epithelial nests are formed during intrauterine life by the mucous membrane covering the alveolar margin projecting into the tissues, where by constriction

FIG. 109.-Multilocular cystoma of the lower jaw; vertical section through tumor, X 176 (after Becker): C, cylindrical cells; P, polygonal cells; Pl, flattened polygonal cells; S, stellate cells; V, vacuoles; Cy, cyst; Pk, pearl-globe (Kugel); K, granular contents of cyst; Ca, capillary from stroma into alveolus; Ck, colloid mass; St, stroma.

at the surface isolation takes place, forming the tooth-germs, and from which buds may form, which serve later as the starting-point of cystoma. Allgayer and Grasse are of the same opinion. Such cysts are lined with epithelial cells, and contain usually a viscid yellowish fluid.

Multilocular cysts of the jaws (Fig. 109) are a great rarity. Re

cently two such cases from the clinic at Bonn were described by Becker. This author found in literature sixteen additional cases. The lower jaw is more frequently the seat of this tumor. From this fact alone it is evident that displaced dental germs are not the cause of these cysts, as most authors claim. In the upper jaw such cysts may rupture into the antrum of Highmore. They are found more frequently in the region of the molar and bicuspid than in that of the other teeth. The youngest patient was twelve years, the oldest seventy-two years of age. The growth, which commences during childhood and puberty, is slow. Trauma and inflammatory affections are the exciting causes. According to the location of the matrix the cyst will project either from the outer or the inner side of the jaw.

The crackling sensation (bruit de parchemin) as a diagnostic sign in the examination of multilocular tumors of the jaw was described by Runge in 1775, and later by Dupuytren. Fluctuation appears when the bony wall has been absorbed, and is consequently a later sign. Ulceration of the gums does not take place. Such tumors often attain an enormous size. Falkson and Bryk describe a case in which the tumor weighed one and a half kilograms and reached from the zygomatic arch to the sternum. On section through the tumor a system of hollow spaces was disclosed. Some of the cysts communicated with others. The septa are usually membranous. These cysts contain a viscid fluid sometimes mixed with blood. The size of the cysts varies from minute spaces to that of a hen's egg. The inner surface of the cysts is smooth. In the study of these cysts three stages are apparent: 1. Cellular cords; 2. Alveoli; 3. Cysts.

XVI. CARCINOMA.

THE subject of carcinoma is one of immense etiological and clinical interest. The etiology has been investigated and discussed for centuries, and, although great progress has been made in tracing the histogenetic origin of carcinoma to its proper source, the explanation of the real cause awaits discovery. The etiology has recently received renewed interest from the bacteriological researches that have been made to prove the microbic origin of carcinoma. As we shall see farther on, no positive proof has been furnished so far that carcinoma is a microbic disease. The clinical interest of carcinoma arises from the prevalence of this affection and the inadequacy of the present surgical resources to cope with it successfully. To what fearful extent carcinoma figures as a cause of death can be learned from the fact that in England and Wales during ten years (1860-1870), 2,379,622 persons above the age of twenty died, and that this number includes 81,699 deaths from carcinoma, the deaths from this cause constituting to all others a ratio of 1:29. There can be but little doubt that this disease is on the increase. The dread of carcinoma is almost universal. Its terrors have been described in prose and in poetry. Shakespeare alludes to it in Hamlet: "And is't not to be damned, to let this canker of our nature come in further evil?" Not only the profession, but also the public, is aware of the great shortcomings of surgery in its treatment. The impression prevails among the people that it is incurable. The great mass of the people have abandoned all hope of the receipt of permanent benefit from the recognized surgical craft for this affection, and seek aid from so-called "cancer specialists" that exist everywhere and fatten on the credulity of an army of despondent, almost desperate, cancer patients. This sad condition of affairs, and with it the remunerative occupation of this horde of pretenders, will cease to exist when the discovery of the real cause of carcinoma is made and when successful therapeutic measures are established upon such basis. The writer has great confidence in future investigations in this direction. A great number of tireless, honest investigators are at work, and the prophesied results will be realized in time.

Definition. Carcinoma is an atypical proliferation of epithelial cells from a matrix of embryonic cells of congenital or post-natal origin.

This definition includes what is known of the histogenetic origin of carcinoma. It refers the tumor to its primary location in mesoblastic tissue, and the origin of its cellular elements to a matrix of embryonic epithelial cells. The heterotopic location of the epithelial cells distinguishes carcinoma from all the benign epithelial tumors. Atypical proliferation of epithelial cells means their growth and multiplication in a locality where epithelial cells have no legitimate citizenship. The matrix may occupy such a location from the very beginning when embryonic cells have been displaced into mesoblastic tissue during the development of the embryo in the case of congenital matrices; or when in a burn or a wound or an inflammatory process embryonic cells become buried in the mesoblast after destruction of the membrana propria in matrices of post-natal origin; or, finally, if the matrix is confined to the epiblastic or hypoblastic tissues, the carcinoma dates back to the time when the embryonic cells passed through and beyond the membrana propria into the vascular mesoblastic tissues.

Views Past and Present regarding the Origin and Nature of Carcinoma.-The old authors were familiar with the gross appearances and the clinical aspects of carcinoma. The division into open and subcutaneous carcinoma was made at an early day; the former was described as cancer apertus, and the latter as cancer occultus. Celsus understood under the term "cancer" the several forms of gangrene. Galen insisted on an early diagnosis, which he based almost exclusively upon its clinical course. Ætius gave an accurate description of carcinoma of the uterus. The classical description of cancer by Soranus. would be no discredit to a modern work on general pathology. All malignant growths were included under the head of cancer. The first attempt to describe tumors upon an anatomical basis was made by Johannes Müller in his work on The Structure of Morbid Growths, published in 1838. Virchow traced the tumor-cells to their histological origin, and thus laid the foundation for a rational classification. He was also the first to describe the alveolar structure of carcinoma, and he called attention to the resemblance of carcinoma-cells to epithelial cells. He believed that both stroma and the epithelial cells were produced by the connective tissue.

The microscope was made available as a means of investigating the structure of tumors by Schleiden and Schwann. Müller in 1836, in a preliminary communication, divided tumors into "benign" and "malignant," by which terms he meant tumors that were curable or incurable by operation. Bichât described carcinoma as a subepithelial tumor, and distinguished a stroma which he believed consisted of degenerated connective tissue and of cells derived from the epithelial layer. Laennec

divided tumors into "homologous" and "heterologous," and among the latter included tubercle, encephaloid, melanosis, and scirrhus. Lobstein, while admitting the correctness of this division, believed that the difference between the two kinds of tumors was due to a species of lymph, which, according to the character of the tumor, is either cuplastic or cacoplastic. Müller maintained that the structure of benign and malignant tumors was identical, and that the classification into homologous and heterologous tumors was based on ignorance of their microscopical structure. He, however, recognized a neoplastic form of cellelements, and in the examination of tumor-tissue under the microscope he speaks of normal tissue, granules, cells, and new connective tissue. From that time dates the description of a morphologically specific caudate cancer-cell which was regarded as the essential element of cancerous infiltration-an opinion which prevailed at his time, but which was not shared by Müller. Lebert and Hannover revived again the theory of the existence of a specific cancer-cell, but, instead of the caudate cell, described a more primitive structure. Lebert separated carcinoma of the skin from carcinoma of internal organs, and called it cancroid. About the same time Ecker examined microscopically three specimens of carcinoma of the lip, and, finding no foreign heteroplastic cells, declared them to be a simple hypertrophy of the papillæ. Mayo discovered general infiltration in a similar tumor, and therefore classified it with what was then generally recognized as cancerous tumors.

Rokitansky classified carcinoma of the skin with glandular carcinoma, and regarded it as a variety of medullary fungus, differing from carcinoma proper only by the form and aggregation of its cells. Lebert modified his views regarding the structure and nature of cancroid after he discovered that in some cases it gave rise to glandular and general infection, and after having found in it the cell-forms which he regarded as characteristic of carcinoma. In 1845 he distinguished three kinds of carcinoma of the skin: 1. Papillary excrescences with inflamed, indurated base and superficial ulceration; 2. Papillary proliferations of the cauliflower kind with enlargement of the sebaceous glands; 3. Epithelial neoplasms consisting of a fibrous framework, its meshes filled with epithelial cells. Ecker, Mayo, and Lebert referred the origin of the new epithelial cells to proliferation from pre-existing mature epithelial cells, while Virchow, Rokitansky, and Neumann claimed that they were the product of metaplastic proliferation of the connective tissue. The glandular origin of carcinoma of the skin was studied by E. H. Weber, and later by Gluge. Ecker, Mayo, Lebert, and Rokitansky believed that carcinoma resulted from tissue-proliferation of the papillæ of the skin. Virchow applied the term cancroid to surface carcinoma