These processes are accompanied by changes in the endothelium of the vessel walls, which result in an increased formation of lymph, which transudes into the meshes of the connective tissue giving rise to an inflammatory oedema, or, if the inflammation is on a free surface, forming an inflammatory exudate.  The quantity and characters of this exudate vary in different parts of the body, and according to the nature, virulence, and location of the organisms causing the inflammation.  Thus it may be serous, as in some forms of synovitis; sero-fibrinous, as in certain varieties of peritonitis, the fibrin tending to limit the spread of the inflammation by forming adhesions; croupous, when it coagulates on a free surface and forms a false membrane, as in diphtheria; haemorrhagic when mixed with blood; or purulent, when suppuration has occurred.  The protective effects of the inflammatory reaction depend for the most part upon the transudation of lymph and the emigration of leucocytes.  The lymph contains the opsonins which act on the bacteria and render them less able to resist the attack of the phagocytes, as well as the various protective antibodies which neutralise the toxins.  The polymorph leucocytes are the principal agents in the process of phagocytosis (p. 22), and together with the other forms of phagocytes they ingest and destroy the bacteria.

If the attempt to repel the invading organisms is successful, the irritant effects are overcome, the inflammation is arrested, and resolution is said to take place.

Certain of the vascular and cellular changes are now utilised to restore the condition to the normal, and repair ensues after the manner already described.  In certain situations, notably in tendon sheaths, in the cavities of joints, and in the interior of serous cavities, for example the pleura and peritoneum, the restoration to the normal is not perfect, adhesions forming between the opposing surfaces.

If, however, the reaction induced by the infection is insufficient to check the growth and spread of the organisms, or to inhibit their toxin production, local necrosis of tissue may take place, either in the form of suppuration or of gangrene, or the toxins absorbed into the circulation may produce blood-poisoning, which may even prove fatal.

#Clinical Aspects of Inflammation.#—­It must clearly be understood that inflammation is not to be looked upon as a disease in itself, but rather as an evidence of some infective process going on in the tissues in which it occurs, and of an effort on the part of these tissues to overcome the invading organisms and their products.  The chief danger to the patient lies, not in the reactive changes that constitute the inflammatory process, but in the fact that he is liable to be poisoned by the toxins of the bacteria at work in the inflamed area.

Since the days of Celsus (first century A.D.), heat, redness, swelling, and pain have been recognised as cardinal signs of inflammation, and to these may be added, interference with function in the inflamed part, and general constitutional disturbance.  Variations in these signs and symptoms depend upon the acuteness of the condition, the nature of the causative organism and of the tissue attacked, the situation of the part in relation to the surface, and other factors.