Page:The Principles and Practice of Medicine.djvu/173



and, or the Practice of Medicine, relates to the prevention, alleviation, and cure of individual diseases. It has, for the most part, reference to the special effects of such diseases upon the part or organ in which they may be situated ; but it also takes cognizance of the gene- ral derangements to which the local disease may lead. Asa knowledge of the phenomena, course, and termination of certain derangements, wherever they may occur, affords a clue to their effects when localised in a particular organ, General Pathology has an important bearing upon Special Pathology.

An individual disease is usually, if not always, an altered state of some of the solid or fluid constituents of the body. It is manifested or made known by certain phenomena, which are the symptoms and signs of it. In some instances it is possible to recognise a material organic change upon which these pheno- mena depend, in which case the " disease" is the altered or abnormal condition of the part or organ. For example, pneu- monia is that condition of the lungs in which the air cells and the intercellular structures are charged with inflammatory exudations pleuritis that condition of the pleura in which the surface of the membrane is more or less covered with flakes of lymph. But in regard to many diseases, we are unable to connect the phenomena presented to our observation with any structural unfitness, and are hence obliged to consider the group of phenomena or symptoms as the " disease" fevers, hysteria, hydrophobia, and tetanus are examples.