Pathologic material is examined in the fresh state when it is desired to make a diagnosis in the shortest time possible, or when the processes of fixation and hardening produce such alterations in the morphology and chemic constitution of the cells that these features can be recognized only in the unfixed, fresh state. So far as the saving of time is concerned it is possible to take material removed during an operation, examine it in the fresh state, and return a diagnosis to the surgeon, while the patient is still on the table under the influence of the anæsthetic. It is not possible to do this with all tissues or with all pathologic conditions; but, when it can be done, the advantages of such a rapid diagnosis, in the saving of time, labor, expense and danger to the patient, are obvious. The best idea of the cell is also gained by its study in a fresh condition. Vital phenomena and certain morphologic features, as cilia, can be observed only in fresh material. Many of the chemic constituents of cells (glycogen, fat, mucin, pseudomucin, albumin-granules, cholesterin, etc.) are either lost, or are so changed by processes of fixation or hardening that they can no longer be recognized. The majority of specific chemic tests can be made in fresh tissues only. Moderate and slight degrees of fatty degeneration and cloudy swelling are easily recognized in the fresh state; in fixed and hardened preparations they may not be recognized at all. Particularly in the case of the heart-muscle is it necessary to make an examination of the fresh material when the diagnosis of these conditions is concerned. Further, a greater or less degree of shrinking is caused by many of the agents used in fixing and hardening, and this is avoided by the examination of the fresh material. In the case of pathologic fluids (sputum, urine, féces, etc.) an examination of the sediment in the fresh state should always be made as a matter of routine. The formed elements of these fluids are best determined by this means. In the case of tissues, a diagnosis made by means of scrapings, smears, teased bits of tissue, frozen sections, etc., should always be controlled by the examination of fixed and hardened material. In the examination of fresh material the following methods are employed: _Sedimentation_, _smears_, _scraping_, _crushing_, _teasing_, _maceration_, _sections_, _shaking or penciling_, _digestion_, _intravital staining_, injection, _the warm stage_ _and_ “_cultivation_.”