appropriate heading. PATHOLOGICAL ANATOMY. CLASSIFICATION. And now to return to the question of morbid anatomy of the thyroid gland, I shall begin by outlining briefly the classification to be used in analyzing our cases, a system which combines those of many pathologists, yet which I believe contains the essentials of all. The changes in the gland being hyperplastic and recessive, at times to a stage of atrophy, no clear cut definite line of demarcation separates all these pictures; instead they must be thought of as merging into one another. When the thyroid enlarges more or less continuously with a maintenance of considerable colloid, the picture is that of COLLOID GOITRE. The gland is pale, gelatinous, tense but resilient and may show large cystic areas with fluid contents. Microscopically studied the acini are overfilled with colloid yet the lining cells are retained but flattened. The cysts may show the ruptured septa of the original acini. Enlarged soft reddish glands are found at times to contain much colloid, nearly every acinus being distended with it, but in such organs the epithelia are high or even reduplicated; the amount of contents is the striking feature. These are termed HYPERPLASIA WITH COLLOID. Hyperplasia may go on with the absorption of colloid, HYPERPLASIA WITHOUT COLLOID. The gland is then a darker body of more solid character, red, dull purple or uniformly pale pink, somewhat dependent upon the blood content. By magnification one sees smaller acini with prominent high cuboidal or cylindrical epithelia and little or no colloid. The increase of cells seems to be due both to an increase in their size and number. As the proliferation increases the lining layer must be accommodated so that it bulges out into the lumen as a bud or papilla which, if it be extensive or universal in the thyroid, gives rise to the ADENOMATOID GOITRE OF PAPILLOMATOUS type. This growth is accompanied by much congestion and small or large hemorrhages may occur, forming cysts containing a blood stained fluid. Grossly such a gland has solid and cystic areas, is mottled red and gray or brown from old pigmentation and is usually of very irregular shape. These forms are more or less uniform and general, but in certain instances the hyperplasia tends to remain in isolated areas or nodules, and in these develop solid masses of thyroid epithelium, sometimes with a small lumen usually devoid of colloid, and a rather rich but loose fibrous supporting tissue, the whole picture resembling the microanatomy of the fetal gland; to these the name fetal adenoma has been given, but since they are not fetal in origin and do not behave like tumors I have called them NODULAR ADENOMATOID HYPERPLASIAS. The next step in hyperplasia would remove it from benign to malignant in pathological character, and the term NEOPLASTIC HYPERPLASIA is used; this must of course be limited to the epithelial growths, since sarcomata, while they occur in the gland, come from other cells.