BLOOD VESSELS, Diseases of the. It is not strange that a tissue subject to such constant use, to all kinds of strains and to the unintermittent influence of a complex, ever changing fluid, bathing its inner coat should be extremely subject to disease and injury. The frame work or base of 'the vascular system is the layer of endothelial cells of which the capillaries are composed almost exclusively. This layer extends through the arterial system on the one and the venous system' on the other, and this portion alone of the blood vessels does not seem to be very susceptible to disease.
The remaining layers of the inner coat and the middle and external coats are all suscept ible and are the seat of disease of various kinds. Diseases which are chiefly regarded as associate! with an abnormal condition of the blood vessels, are rheumatism, gout, syphilis, chronic alcoholism, Bright's disease and the structural changes which come with old age.
One of the most common forms of disease in blood vessels arises from the formation of a clot in the vessels. This is the way a vessel is plugged after an injury or after it has been tied by the surgeon with a ligature. The cut ting off the circulation in the area supplied by the vessel is like depriving the soil of mois ture, and unless the tissue in question is sup plied by neighboring vessels which make new channels to take the place of those which have been obliterated, its nutrition suffers greatly. If the vessel is one of considerable size or if it is a terminal vessel, the tissue dies and experiences gangrene or decomposition.
This is what happens not infrequently in the lower extremities, especially in the aged, and in the disease known as diabetes, one or more of the toes or even the entire foot be comes gangrenous and requires amputation. A plug of this kind is called a thrombus, and the disease thrombosis and may occur either in arteries or veins. Besides the terminal arteries of the lower extremities which are thus diseased this condition occurs in the terminal arteries of the kidneys, lungs, spleen and brain, with more or fewer ruptures, hemorrhages and destruction of tissue.
Friability or brittleness of the arteries is also a frequent form of disease, and particu larly also in the aged. This is the condition known as arterio-sclerosis, when there may be a formation of new connective tissue in the arteries increasing their density, or a deposit of mineral salts, especially of lime, causing them to break easily. Both of these conditions often terminate in cerebral hemorrhage or apoplexy.
A very common form of disease affecting arteries in particular, but sometimes veins, and sometimes resulting, in communication between an artery and a vein and the commingling of blood currents, is aneurism, in which one or more of the inner coats gives way, forming a larger or smaller tumor or bulge of the vessel. If this tumor ruptures, hemorrhage takes place into the surrounding tissue until there is sufficient pressure or a sufficiently dense clot to arrest it. In the case of large arteries or arteries in vital structures like the brain the hemorrhage is not infrequently fatal. Arteries that are diseased from syphilis or that are deficient in elastic or muscular tissue, or those that are subject to frequent and powerful strain, are often the seat of aneur ism, and athletes, porters, truckmen and others who bear heavy weights are frequently victims.
Blood vessels like other tissues are supplied with vessels, nerves and lymphatics for their nourishment and their functional activity. The nerve supply, especially that of the small arter ies, is of very great importance, consisting of 'vaso-dilator fibres from the cerebro-spinal and vaso-inhibitory fibres from the sympathetic system. When one or the other apparatus of this kind is diseased or out of order there is disturbance in the circulation of the vessels involved and in the tissues they supply, paraly sis of the inhibitory nerves, meaning dilatation of .the blood vessels and congestion of the tissues, and paralysis of the dilator nerves, meaning constriction of blood vessels and ane mia and pallor of the tissues.