Thomas Gregor Brodie

“ Upon examining a drop of this mixture a number of bacteria are found within the phagocytes. Thus this attack and destruction of bacteria by phagocytes may take place within the body or by cells removed from the body. Whether or no a phagocyte can engulf bacteria is dependent upon a number of factors—partly specific properties of the phagocyte, partly factors varying with the constitution of the body serum. Thus Wright and Douglas, employing Leishman’s method, have proved that leucocytes do not take up bacteria freely unless the serum in which they are suspended contain opsonins. ”

“ Analogous changes are observed in the tissues of a mammal when blood which has been extravasated is being removed, e.g. after a bruise. The first effect of the haemorrhage is an exudative inflammation, during which leukocytes arrive in large numbers and engulf the corpuscles. In the process of digestion which follows the haemoglobin is altered and new pigments formed from it. In mammals this pigment is dark red or brownish, in the pigeon it is green. ”

“ It is readily understandable that we should find such cells on the external surface of an organism or on the surface lining the alimentary tract, particularly in the latter position. But in addition there are many cells within the body in which phagocytic power is retained and markedly developed. Such cells may be fixed or wandering cells. ”

“ They have been attracted to the damaged area. The mechanism which effects this attraction is a chemical one—chemiotaxis. At the seat of the change chemical substances are produced which act upon the phagocytes, causing them to migrate towards the source—positive chemiotaxis. Apparently the material dissolving from cell débris can act in this manner. Thus if a capillary tube filled with a tissue extract be inserted under the skin of an animal, within a short time it will be found to be surrounded with numbers of leucocytes, which may also have encroached into the tube itself. ”