during his lifetime and amassed a considerable fortune. He built himself in 1547 a fine house in Arezzo, and spent much labour in decorating its walls and vaults with paintings. He was elected one of the municipal council or priori of his native town, and finally rose to the supreme office of gonfaloniere. He died at Florence on the 27th of June 1571.
Personally Vasari was a man of upright character, free from vanity, and always ready to appreciate the works of others: in spite of the narrow and meretricious taste of his time, he expresses a warm admiration of the works of such men as Cimabue and Giotto, which is very remarkable. As an art historian of his country he must always occupy the highest rank. His great work was first published in 1550, and afterwards partly rewritten and enlarged in 1568, bearing the title Delle Vite de’ piu eccellenti pittori, scultori, ed architettori. It was dedicated to Cosimo de’ Medici, and was printed at Florence by the Giunti; it is a small quarto illustrated with many good woodcut portraits. This editio princeps of the complete work is usually bound in three volumes, and also contains a very valuable treatise on the technical methods employed in all branches of the arts, entitled Le Tre Arti del disegno, cioè architettura, pittura, e scoltura. His biographies are written in a very pleasant style, interspersed with amusing stories. With a few exceptions Vasari’s judgment is acute and unbiased. And though modern criticism—with all the new materials opened up by research—has done valuable work in upsetting a good many of his traditional accounts and attributions, the result is a tendency very often to underestimate Vasari’s accuracy and to multiply hypotheses of a rather speculative character. The work in any case remains a classic, however it may be supplemented by the more critical research of modern days.
Vasari gives a sketch of his own biography at the end of his Vite, and adds further details about himself and his family in his lives of Lazzaro Vasari and Francesco Salviati. The best edition of Vasari’s works is that published at Florence by Milanesi (1878–1882), which embodies the valuable notes in the earlier edition by Le Monnier (1846); another, by Venturi, was begun in 1896. The Lives has been translated into French, German and English (by Mrs Foster, London, 1850).
VASCULAR SYSTEM. I. Anatomy.—The circulatory or
blood vascular apparatus consists of the central pump or heart, the arteries leading from it to the tissues, the capillaries, through the walls of which the blood can give and receive substances to and from the tissues of the whole body, and the veins, which return the blood to the heart. As an accessory to the venous system, the lymphatics, which open finally into the great veins, help in returning some of the constituents of the blood. Separate articles are devoted to the heart, arteries, veins and lymphatic system, and it only remains here to deal with the capillaries.
The blood capillaries form a close network of thin-walled tubules from 12000 to 13000 of an inch in diameter, permeating, with a few exceptions, the whole of the body, and varying somewhat in the closeness of its meshwork in different parts In the smallest capillaries, in which the arteries end and from which the veins begin, the walls are formed only of somewhat oval endothelial cells, each containing an oval nucleus and joined to its adjacent cells by a serrated edge, in the interstices of which is a small amount of inter cellular cement, easily demonstrated by staining the preparation with nitrate of silver. Here and there the cement substance is more plentiful, and these spots when small are known as stigmata, when large as stomata. As the capillaries approach the arteries on the one hand and the veins on the other they blend and become larger, and a delicate connective tissue sheath outside the endothelium appears, so that the transition from the capillaries into the arterioles and Venules is almost imperceptible; indeed, the difference between a large artery or vein and a capillary, apart from size, is practically the amplification and differentiation of its connective tissue sheath.
Embryology.—The first appearance of a vascular system is outside the body of the embryo in the wall of the yolk sac, that is to say, in the mesoderm or *the middle one of the three embryonic layers. The process is a very early one and in the chick is seen to begin at the end of the first day of incubation. The first occurrence is a network made up of solid cords of cells forming in certain places solid cell masses called the blood islands of Pander; The central cells of these islands divide by karyokinesis and gradually float away into the vessels which are now being formed by fluid from the exterior, finding its way into the centre of the, cell cords and pressing the peripheral cells flat to form the endothelial lining. These free cells from the blood islands are known as erythroblasts and are the primitive corpuscles of the foetal blood. They have a large reticular nucleus and at first are colourless though haemoglobin gradually develops within them and the blood becomes red (see Blood). The erythroblasts continue to multiply by karyokinesis in early foetal life, especially in the liver, spleen, bone marrow and lymphatic glands, though later on their formation only occurs in the red bone marrow. In most of the erythroblasts the nucleus soon becomes contracted, and the cell is then known as a normoblast, while ultimately the general view is that the nucleus disappears by extrusion from the cell and the non-nucleated red blood plates or erythrocytes remain. The leukocytes or white blood corpuscles appear later than the red, and are probably formed from lymphoid tissue in various parts of the body. The blood vessels thus formed in the so-called vascular area gradually travel along the vitelline stalk into the' body of the embryo, and two vessels larger 'than the rest are formed one on each side of the stalk. These are the vitelline veins, which, as they pass towards the caudal end of the embryo, become the two primitive aortae, and these fuse later on to form the heart. After the inversion of the pericardia region and formation of the head fold (see Coelom and Serous Membranes) the front of the developing heart becomes the back, and the Vitelline veins now enter it from behind. It must be understood that most of our knowledge of the early history of the blood vessels is derived from the study of lower mammals and birds, and that this is being gradually checked by observations on human embryos and on those of other primates. It seems probable that in these mammals; owing to the small size of the yolk sac, the vessels of the embryo establish an early communication with those of the chorion before the vitelline veins are formed (see Quain’s Anatomy, vol. i., London, 1908). The later stages of the embryology of the vascular system are sketched in the articles on Heart, Arteries, Veins and Lymphatic System (q.v.). (F. G. P.)
II. History of Discovery
Galen, following Erasistratus (ob. 280 B.C.) and Aristotle, clearly distinguished arteries from veins, and was the first to overthrow the old theory of Erasistratus that the arteries contained air. According to him, the vein arose from the liver in two great trunks, the vena porta andGalen. vena cava. The first was formed by the union of all the abdominal veins, which absorbed the chyle prepared in the stomach and intestines, and carried it to the liver, where it was converted into blood. The vena cava arose in the liver, divided into two branches, one ascending through the diaphragm to the heart, furnishing the proper veins of this organ; there it received the vena azygos, and entered the right ventricle, along With a large trunk from the lungs, evidently the pulmonary artery. The vena azygos was the superior vena cava, the great vein which carries the venous blood from' the head and upper extremities into the right auricle. The descending branch of the great trunk supposed to originate in the liver was the inferior vena cava, below the junction of the hepatic vein. The arteries arose from the left side of the heart by two trunks, one having thin walls (the pulmonary veins), the other having thick walls (the aorta). The first was supposed to carry blood to the lungs, and the second to carry blood to the body. The heart consisted of two ventricles, communicating by pores in the septum; the lungs were parenchymatous organs communicating with the heart by the pulmonary veins. The blood-making organ, the liver, separates from the blood subtle vapours, the natural spirits, which, carried to the heart, mix with the air introduced by respiration, and thus form the vital spirits; these, in turn carried to the brain, are elaborated into animal spirits, which are distributed to all parts of the body by the nerves.[1] Such were the views of Galen, taught until early in the 16th century.
Jacobus Berengarius of Carpi (ob. 1530) investigated the structure of the valves of the heart. Andreas Vesale or Vesalius (1514–1564) contributed largely to anatomical knowledge, especially to the anatomy of the circulatory organs. He determined the position of the heart in the chest;Vesalius.
- ↑ See Burggraeve’s Histoire de l’anatomie (Paris, 1880).
