The _swelling_ is partly due to the increased amount of blood in the affected part and to the accumulation of leucocytes and proliferated tissue cells, but chiefly to the exudate in the connective tissue--_inflammatory œdema_. The more open the structure of the tissue of the part, the greater is the amount of swelling--witness the marked degree of œdema that occurs in such parts as the scrotum or the eyelids. _Pain_ is a symptom seldom absent in inflammation. _Tenderness_--that is, pain elicited on pressure--is one of the most valuable diagnostic signs we possess, and is often present before pain is experienced by the patient. That the area of tenderness corresponds to the area of inflammation is almost an axiom of surgery. Pain and tenderness are due to the irritation of nerve filaments of the part, rendered all the more sensitive by the abnormal conditions of their blood supply. In inflammatory conditions of internal organs, for example the abdominal viscera, the pain is frequently referred to other parts, usually to an area supplied by branches from the same segment of the cord as that supplying the inflamed part. For purposes of diagnosis, attention should be paid to the terms in which the patient describes his pain. For example, the pain caused by an inflammation of the skin is usually described as of a _burning_ or _itching_ character; that of inflammation in dense tissues like periosteum or bone, or in encapsuled organs, as _dull_, _boring_, or _aching_. When inflammation is passing on to suppuration the pain assumes a _throbbing_ character, and as the pus reaches the surface, or "points," as it is called, sharp, _darting_, or _lancinating_ pains are experienced. Inflammation involving a nerve-trunk may cause a _boring_ or a _tingling_ pain; while the implication of a serous membrane such as the pleura or peritoneum gives rise to a pain of a sharp, _stabbing_ character. _Interference with the function_ of the inflamed part is always present to a greater or less extent. #Constitutional Disturbances.#--Under the term constitutional disturbances are included the presence of fever or elevation of temperature; certain changes in the pulse rate and the respiration; gastro-intestinal and urinary disturbances; and derangements of the central nervous system. These are all due to the absorption of toxins into the general circulation. _Temperature._--A marked rise of temperature is one of the most constant and important concomitants of acute inflammatory conditions, and the temperature chart forms a fairly reliable index of the state of the patient. The toxins interfere with the nerve-centres in the medulla that regulate the balance between the production and the loss of body heat.