1148 PHYSIOLOGY 



the whole leucocyte passes through and lies in the lymph spaces outside 

 the capillary. In the course of five or six hours all the capillaries and 

 small veins in the neighbourhood of the injury may show a crowd of 

 leucocytes along their outer surfaces. The use of this emigration 

 seems to be to remove the tissue injured by the primary lesion. As 

 soon as this is effected, regeneration of the injured tissue occurs by a 

 proliferation of the connective-tissue corpuscles and the epithelium, 

 while the leucocytes move away and disappear. The essential phago- 

 cytic character of the inflammatory process may be shown if the 

 primary lesion be attended with infection. Thus if a small quantity 

 of the staphylococcus be injected into the subcutaneous tissue of the 

 rabbit, the vessels surrounding the point of injection within four hours 

 may be found densely filled with corpuscles. In ten hours' time 

 the leucocytes are present in large numbers outside the vessels, while 

 the injected cocci have spread for some distance along the lymphatic 

 spaces and, while partly free, have been to a large extent ingested by 

 the leucocytes. In twenty hours' time the connective-tissue fibrils at 

 the point of injection are found to be widely separated by the aggrega- 

 tion of leucocytes. In forty-eight hours' time a well-defined abscess is 

 produced. At the centre all traces of previous connective tissue have 

 disappeared and its place has been taken by a dense mass of leucocytes, 

 many in a state of degeneration, mingled with staphylococci, partly 

 within, partly outside the cells. The margin of the abscess is formed 

 by connective tissue infiltrated with living leucocytes. A certain 

 number of cocci are to be seen free in the tissue outside this layer, but 

 in the course of a day or two these free cocci disappear, and there is 

 thus a continuous layer of phagocytes surrounding the abscess cavity 

 and preventing any further invasion of the body as a whole from the 

 seat of infection. The abscess subsequently discharges on to the 

 exterior by a process of necrosis of the superjacent skin, and regenera- 

 tion of tissue takes place in the same manner as in the more trivial 

 injury. Inflammation in warm-blooded animals thus gives rise to 

 dilatation of vessels and increased vascularity of a part, to alteration 

 of the vessel- wall, and therefore to increased effusion of fluid. There 

 are increased warmth and redness of the part from the vascular dilata- 

 tion, swelling from the increased diffusion of lymph, and very often, 

 as a result of the injury or the swelling and the consequent involve- 

 ment of sensory nerves, pain. The four cardinal symptoms of 

 inflammation, namely, rubor, color, turgor, and dolor, which have been 

 described for generations as typical of this condition, leave out of 

 account altogether the phenomenon which Waller's and Cohnheim's 

 observations, in the light of the comparative studies of Metchnikoff, 

 have shown us to be the essential feature of the process, namely, phago- 

 cytosis, the accumulation of wandering mesoderrn cells round the seat 



