The adult or third stage of development, can only be attained within the intestinal canal of the dog or wolf. These animals devouring a sheep or other ruminant, or in some rare case perhaps a human being, within which the hydatid has been formed, the cysts thus taken into the stomach, develop into the perfect worm, from which segments containing the eggs are again discharged. It would appear almost impossible for the embryo from these eggs, to ever enter the human stomach, but it is not difficult to understand that the fæces of the dog containing the ova, may enter a spring or stream, from which the minute embryo may be taken with the water, by either man or a lower animal; or, by attaching themselves to watercresses, etc., they may be eaten with these by the same. _Hydatid tumors_ of the liver, may vary, greatly, in size, according to their age. From an extremely minute cyst, they may acquire such a size as to fill and distend the abdominal cavity, crowding the several viscera from their position. There may be one or several. They may be confined to the liver, or secondary cysts may appear in other organs. When opened, the interior is generally filled with numerous smaller cysts of various sizes, each filled with a gelatinous fluid of varying degrees of density and color, and within which, by a careful microscopic examination, may be detected—many times, not always—numerous hooklets, which have been detached from the minute heads. The walls of the parent cyst may become greatly thickened, or even calcified. The contents may degenerate into a purulent mass, with which may be mingled blood or bile. The development of these tumors is usually slow, and unattended with pain, or functional disturbance of the liver. After they have acquired a large size, they may induce peritonitis, resulting in extensive adhesions. Rupture of these hydatids sometimes take place, this accident being followed by death, or recovery, according to the point at which the rupture takes place. They may burst in the following directions: 1. Through the diaphragm into the pleural cavity, or into the substance of the lungs. 2. Rarely into the pericardium. 3. Into the peritoneal cavity, resulting in acute peritonitis. 4. Through the abdominal walls, when recovery is possible. 5. Into the stomach or intestines; this being the most favorable point of rupture. In fifteen cases of rupture into the intestines, fourteen recovered. 6. Into the biliary passages or large blood-vessels. CASE.—_Large Hydatid Tumor of the Liver—Death from Exhaustion._ Mr. O——, of this city, aged 75 years, noticed some two years previous to his death that his abdomen was enlarging. An examination disclosed the presence of a large tumor descending from the region of the liver. It was slightly fluctuating, and unattended with pain or soreness. He complained of nothing but weakness with vertigo. All the functions of the body were natural.