Myxoma is a tumor in which mucoid elements or a gelatinoid degeneration and infiltration containing mucin is a prominent feature. The _mucous tissue_ which constitutes the tumor may differ little from ordinary connective tissue except that the intercellular spaces contain mucin. Histologically the tissue consists of cells embedded in a homogeneous matrix. The cells may be of various forms, round, (in recent formations) and spindle-shaped or star-shaped, but especially the latter, in the older. When incised a fluid containing mucus escapes in greater or less abundance. While this has properties resembling albumen it is distinguished by the fact that the precipitate thrown down in it by alcohol is softened and redissolved on the addition of water. The precipitate thrown down in an albuminous liquid is insoluble in water. The formation of this mucous exudate is liable to be followed by fat so that Virchow considered it as antecedent to fat formation. This is especially noticeable in the early stages of the cholesteatomata of the choroid plexus of the horse, in which, as observed by Fürstenberg, Lassaigne, and Verheyen, the new formation is at first a myxoma, which later becomes filled up with cholesterine. Recent observations tend to discredit the alleged distinctive character of myxoma. The meshes of all connective tissue contain a perceptible amount of mucin. Œdematous subcutaneous connective tissue contains this mucin in greater proportion and approximates to the condition of mucous tissue. The umbilical cord, which has been long advanced as the physiological type of mucous tissue, has been shown to consist of ordinary connective tissue with an abundance of fluid in its meshes. Koster denies that the myxoma is a special type of tumor, and holds that it is only a condition that may arise in any tumor which contains connective tissue. In other words, myxoma is only an œdematous condition of the connective tissue neoplasm—fibroma, sarcoma, carcinoma, etc.—due to passive congestion or other circulatory disturbance. As seen in the brain of the horse the formation is usually of the nature of a myxo-lipoma, as the final outcome is usually the cholesterine bearing mass. In other cases the connective tissue spaces become further distended with the viscous, gelatinoid liquid and form veritable cysts—myxoma-cystoides. In tumors of this kind affecting the choroid plexus the chain of symptoms is essentially the same as given under cholesteatoma and the prognosis is nearly equally grave. It need only be said that in recent cases in which there is as yet little permanent tissue, measures may sometimes be hopefully adopted, to secure the reabsorption of liquid constituents, and even perchance to remove some obvious cause of passive congestion upon which the effusion depends. ACROMEGALY. HYPERTROPHY OF THE PITUITARY BODY.