. Elements of human physiology. Physiology. THE VASCULAR MECHANISM 281 which large numbers of leucocytes are present, and which remains almost stationary ; and an inner layer of slowly moving red corpuscles. Since this slowing of the circulation is unattended by any narrowing of the calibre of the vessels, it must be due to an increased friction between the blood- plasma and its contents and the capillary wall. It has been explained by saying that the layer of endothelium is more adhesive. In the capillaries the endothelium is also thickly covered with leucocytes, but here the red corpuscles a
. Elements of human physiology. Physiology. THE VASCULAR MECHANISM 281 which large numbers of leucocytes are present, and which remains almost stationary ; and an inner layer of slowly moving red corpuscles. Since this slowing of the circulation is unattended by any narrowing of the calibre of the vessels, it must be due to an increased friction between the blood- plasma and its contents and the capillary wall. It has been explained by saying that the layer of endothelium is more adhesive. In the capillaries the endothelium is also thickly covered with leucocytes, but here the red corpuscles are mixed with the leucocytes, and there is not such a division into two layers as in the veins. Very soon, at one or two spots, it will be observed that a leucocyte is squeezing itself or being squeezed through the capillary wall, so that half of it lies inside, half of it outside the vessels, and the emigra- tion speedily becomes complete. This emigration of white Fig. Emigration of leucocytes through capillary wall. (Arnold.) blood-corpuscles increases in extent, and at the end of seven or eight hours the tissues in the immediate neighl;ourhood of the small veins and capillaries are infiltrated with masses of leucocytes. At the same time the amount of lymph that transudes through the vessel-walls is largely increased, so that it cannot be carried off quickly enough by the lymphatics, and remains in the interstices of the tissues, causing a swelling or oedema. The true significance of this process of inflammation has been pointed out in recent years by Metchnikoft'. This observer has shown that all the vascular phenomena of in- flammation are directed towards furthering the emigration of leucocytes, and that these leucocytes, or â pliagocytes, have the power of devouring the irritant body if it be a micro-organism, or of removing the tissues killed by the lesion, and so clearing the ground for a regeneration of the tissue. It is probable. Please note that these images a
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