WITH 12 TEXT FIGURES.Although considerable attention has been given of late to the study of the development of lymph glands, only two writers have led up to the discovery of the origin of the lymphatic system as a whole, Budge and Ranvier.* In 1880 Budge published an account of a canal system which he had discovered in the mesoderm of early chick embryos; and in 1887, after Budge's death, His published a further but necessarily incomplete account of this work from Budge's notes and pictures.Budge injected the false amnion of chicks three days old, and found that the fluid ran out into the area vasculosa as if in ducts. He then injected along the arteries in chicks from nine to eighteen days old and obtained beautiful injections of undoubted lymphatics. These two experiments are related to one another in the text by the following theory: Budge thought that there were two lymphatic systems, and that the first or primitive system was present in the three-day chick. He thought that the false amnion and ccelom being continuous, there were ducts within the body wall connected with the c d o m , analogous to those of the area vasculosa which he had injected from the false amnion. The ducts within the body lying along the dorsal line became pinched off from the ccelom and united to form a thoracic duct. With the thoracic duct began the second o r permanent lymphatic system, which he had injected along the arteries in nine-day chicks. This idea of relating the lymphatic system to the serous cavities has remained but a theory and the gap between the two systems of Budge has never been filled.

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The question of the origin of the vascular system can be solved by the method of studying the living blastoderm of the chick in hanging-drop preparations.By watching chicks of the second day of incubation in these preparations it is possible to see all the processes by which blood-vessels and later blood-cells form. These observations can be made best on the area pellucida. Blood-vessels begin by the differentiation from mesoderm of a new type of cells, angioblasts or vaso-formative cells. They differ from mesoderm in having a much more granular cytoplasm and in being more refractile. They differ also in their behavior and in their potentialities. When a cell of the mesoderm divides, the daughter cells separate at least enough so that they can be recognized as distinct cells but angidblasts give daughter cells that remain together to form dense syncytial masses. These small masses soon join similar masses by means of tiny processes of cytoplasm put out from them exactly like the sprouts by which blood-vessels are known to grow. In this way angioblasts form a plexus of dense masses of cells in sharp contrast to the more delicate plexus of mesoderm which represents the early stages of the development of the coelom. The plexus of angioblasts increases both by the division and the growth of its cells and by the constant addition of new angioblasts which differentiate from the mesoderm.

1. The early reaction to intravenous tubercular infection in the various organs of the rabbit reveals a pathognomonic response in the lungs within 24 hours; the specific response in the liver, spleen, lymph glands, and bone marrow, follows from the 6th to the 14th days. 2. The development and extent of the pathologic process has been analyzed in terms of the activity of monocytes and clasmatocytes. 3. The criteria for differentiating these mononuclear phagocytic cells into two strains have been analyzed and the technics discussed. 4. The clasmatocyte phagocytizes tubercle bacilli freely and fragments them, as it does all cellular and other debris. 5. The monocyte stimulated to metamorphose into the typical epithelioid and giant cell of the Langhans type retains the tubercle bacilli intact, with power to survive and multiply, over long periods of time. 6. The normal number of monocytes or the degree to which monoblasts may be stimulated to development and maturation, together with the activity of the clasmatocytes in destroying bacilli, in any particular region, would appear to be a function of the rapidity and extent of the local tubercular involvement.

It has long been known that antibodies are almost invariably associated with th~ globulin fractions in the serum. An example of this association in the case of antipneumococcus serum was presented some years ago by Avery (1). Furthermore: within the last decade, evidence that antibodies are themselves protein has been steadily accumulating. Especially convincing have been the studies of Felton and his collabo. rators (2, 3) on the concentration and purification of the antibodies in antipneumococcus horse sera and the extension of these studies by Chow and Goebel (4). However, without quantitative micro methods for the estimation of antibodies in absolute terms the identification of antibodies as modified serum globulins would necessarily have remained uncertain. The development of such methods by Heidelberger and his collaborators (5) and the extension of their theoretical studies to the preparation of more highly purified antibody than had previously been obtainable led to accurate investigations on the physical-chemical properties of antibodies by the ultracentrifugal (6-9) and electrophoretic (10, 11) methods. Since the molecular weights and electrical mobilities found were those characteristic of proteins, the identification of antibodies as modified serum globulins may be considered accomplished. A chemically satisfactory theory of antibody formation has been put forward by Breinl and Haurowitz (12) and was restated by Mudd (13).All of this chemical work signifies that the cellular mechanisms which give rise to antibodies must be concerned in their normal functions with the synthesis of globulin. For some years evidence has been presented implicating the cells of the reticulo-endothelial system in the formation of antibodies. The present report seeks to make our understanding of the mechanism of this function more definite.Studies of the reactions of the phagocytic mononuclear cells stem from the work of Ehrlich and Metchnikoff. It is known that when Ehrlich was experimenting with dyes, he suggested to his friend Goldmann that he use pyrrol blue for observations on these cells. Goldmann (14) then made a survey of all the cells in the body which will phagocytize azo dyes given in the form of particulate matter. His work was followed by that of Aschoff (15) and of Kiyono (16) who used carmine particles, and by that of Evans and his associates (17-19) who employed trypan blue. Aschoff formulated the concept 67on May 7, 2018 jem.rupress.org Downloaded from