STUDIES ON INFLAMMATION : VI. FIXATION OF TRYPAN BLUE IN INFLAMED AREAS OF FROGS

Trypan blue injected into the circulating blood stream of frogs accumulates rapidly in an inflamed area. When trypan blue is injected directly into the area of inflammation it is fixed in situ and fails to diffuse outward. If the dye is injected at the periphery of an inflamed area it fails to enter the site of inflammation. This failure of penetration is caused by the occlusion of lymphatic vessels and the presence of a network of fibrin in the inflamed area. These experiments furnish additional evidence that fixation of foreign substances by the inflammatory reaction is due to mechanical obstruction caused by a network of fibrin and by thrombosed lymphatics at the site of inflammation.     

STUDIES ON INFLAMMATION : VIII. INHIBITION OF FIXATION BY UREA. A FURTHER STUDY ON THE MECHANISM OF FIXATION BY THE INFLAMMATORY REACTION

A concentrated urea solution effectively dissolves fibrin. The injection into the peritoneal cavity of a urea solution (30 or 50 per cent) together with or after an inflammatory irritant (aleuronat) prevents wholly or in part the local fixation of graphite particles or ferric chloride introduced subsequently. The histologic picture in the retrosternal lymphatics explains how this comes about. When free dissemination of graphite to the retrosternal nodes occurs, the lumen of the lymphatic vessel is unobstructed, whereas partial dissemination is accompanied by small fibrinous thrombi occluding the lumen in part only. Trypan blue injected at the periphery of an inflamed skin area treated with a concentrated urea solution and bacteria (Staph. aureus) penetrates readily into the area, whereas it fails to do so when introduced around an inflamed area consequent on the injection of distilled water and bacteria (Staph. aureus). Concentrated urea per se is an inflammatory irritant. Graphite particles injected into a peritoneal cavity previously treated with concentrated urea penetrate freely to the retrostemal lymphatic nodes; the lymphatic vessel is relatively unobstructed. Trypan blue injected into the circulating blood accumulates rapidly in cutaneous areas almost immediately after the latter have been treated with concentrations of urea ranging from 50 per cent down to 20 per cent. The results of this study furnish evidence, in addition to that already provided, that fixation of foreign substances is primarily due to mechanical obstruction caused by a fibrin network and by thrombosed lymphatics at the site of inflammation. The significance of fixation in relation to immunity and its bearing upon some of the other processes involved in the inflammatory reaction have been stressed.     

STUDIES ON INFLAMMATION : VII. FIXATION OF BACTERIA AND OF PARTICULATE MATTER AT THE SITE OF INFLAMMATION

India ink or graphite partides injected into an area of inflammation fail to disseminate to the tributary lymph nodes. When injected into a normal peritoneal cavity they rapidly appear in the retrosternal lymph nodes. When injected into an inflamed peritoneal cavity they are fixed in situ and fail to reach the regional lymph nodes. Graphite particles injected in the circulating blood stream enter an inflamed area both as free particles owing to increased capillary permeability and also as phagocyted material within leucocytes. Bacteria (B. prodigiosus) injected into inflamed tissue are fixed at the site of inflammation and fail to disseminate to the regional lymph nodes as readily as when injected into normal tissue. Bacteria (B. prodigiosus) injected at the periphery of an inflamed area do not readily penetrate into the site of inflammation. The experiments furnish evidence, in addition to that already provided, that fixation of foreign substances by the inflammatory reaction is primarily due to mechanical obstruction caused by a fibrin network and by thrombosed lymphatics at the site of inflammation. Bacteria (B. prodigiosus and B. pyocyaneus) injected intravenously rapidly enter an inflamed area. It is suggested that localization of bacteria in a locus minoris resistentiae may be explained as the result of increased capillary permeability with subsequent accumulation and fixation of bacteria from the blood stream at the point of injury.     

STUDIES ON INFLAMMATION : V. THE MECHANISM OF FIXATION BY THE INFLAMMATORY REACTION

Microscopic studies show the presence of a network of fibrin within the tissues and numerous thrombosed lymphatics at the site of inflammation. Precipitated iron compounds, possibly coagulated horse serum, or particulate matter caught in this fibrinous reticulum will disseminate less readily than trypan blue from the site of inflammation. Trypan blue injected at the periphery of an inflamed area fails to enter the site of inflammation. This failure of penetration is caused by the occlusion of lymphatic vessels and by the presence of a fine network of fibrin in the tissue spaces of the inflamed area. Fixation of foreign substances by the inflammatory reaction is therefore primarily due to mechanical obstruction caused by a network of fibrin and by thrombosed lymphatics at the site of inflammation. There is another phase of the problem which still requires more accurate information. This concerns the relation between exudation from blood vessels and changes in flow of lymph from the inflamed area. Further experiments are being conducted to investigate this question. The reaction of fixation which occurs extremely early in the inflammatory process circumscribes the irritating substance and allows a definite period of time for the leucocytes to assemble for the purpose of phagocytosis. It is through a delicate regulating mechanism of this kind that, to use the expression of Opie (7), "the vital organs are protected at the expense of local injury."     

STUDIES ON INFLAMMATION : I. FIXATION OF VITAL DYES IN INFLAMED AREAS

Trypan blue injected into normal subcutaneous tissue passes rapidly to the regional lymphatic node and is found in lymph drawn from its efferent lymphatic. When the dye is injected into the normal peritoneal cavity it rapidly appears in the lymph of the retrosternal lymphatics and stains deeply the retrosternal lymphatic nodes. Trypan blue injected into the site of inflammation in the subcutaneous tissue or in the peritoneal cavity is fixed in the inflamed area and fails to reach the regional lymphatic nodes. If an inflammatory reaction has been produced in the dermis or in the subcutaneous tissue, trypan blue injected into the circulating blood enters the site of inflammation and is fixed so that the tissues are deeply stained.     

STUDIES ON INFLAMMATION : IV. FIXATION OF FOREIGN PROTEIN AT SITE OF INFLAMMATION

Foreign protein such as horse serum injected into an inflamed peritoneal cavity penetrates into the blood stream less rapidly than when introduced into the normal cavity. Foreign protein injected into a cutaneous inflammatory area is held in situ for a longer period than when injected into an inflamed peritoneal cavity. Foreign protein introduced into the circulating blood stream accumulates in an inflamed area, where it is found in greater concentration than in normal tissue. Accumulation of foreign protein at the site of inflammation explains the phenomenon of local anaphylaxis described by Auer in rabbits sensitized to horse serum. The antigen accumulating in the inflamed ear reacts with antibody, intensifies a pre-existing inflammatory reaction and produces necrosis of the ear.     

STUDIES ON THE MECHANISM OF IMMUNITY IN TUBERCULOSIS : THE R?LE OF EXTRACELLULAR FACTORS AND LOCAL IMMUNITY IN THE FIXATION AND INHIBITION OF GROWTH OF TUBERCLE BACILLI

1. The fate of bacilli of reinfection at the portal of entry and in metastatic foci, and also the associated host responses, are essentially similar in rabbits and guinea pigs. 2. However, in the guinea pig tubercle bacilli of reinfection are more effectively fixed at the portal of entry than in the rabbit. 3. The guinea pig fixes at the site of reinfection unrelated substances, such as trypan blue and agar particles, more effectively than the rabbit. 4. At the site of a local non-specific inflammation precipitins from the circulating blood accumulate in higher concentration in tuberculous guinea pigs than in tuberculous rabbits. 5. These differing fixing capacities of the two species are associated with differences of extracellular character in the inflammation resulting from reinfection. (a) In the guinea pig, whose tissues are highly sensitized and greatly injured by the tubercle bacillus, the lymphatics adjoining the site of reinfection become thrombosed. In the rabbit whose tissues are moderately sensitized and less injured by the tubercle bacillus the corresponding lymphatics remain open. (b) In the guinea pig the fibrinous network at the site of inflammation forms a fine sieve-like structure. In the rabbit this network forms a coarse sieve-like barrier. 6. In rabbits and guinea pigs primarily infected, the destruction of tubercle bacilli takes place first and most extensively at the portal of entry. At this time they are less effectively destroyed in the nearest metastatic foci. Simultaneously they are still growing without hinderance in such foci in remote internal organs. 7. The cell-free body fluids of normal animals support the growth of tubercle bacilli in vivo. The body fluids of tuberculous animals under the same conditions are bacteriostatic for this microorganism. 8. Tubercle bacilli often multiply by preliminary subdivision into non-acid-fast granules, from which the acid-fast rods sprout. This confirms the work of Kahn.     

SEVERE ACTIVE CUTANEOUS HYPERSENSITIVITY IN THE RAT PRODUCED BY HEMOPHILUS PERTUSSIS VACCINE

Hemophilus pertussis vaccine injected into normal rat skin produced local edema lasting several days. Four to 6 days later the injected site became severely inflamed. When uninjected skin was challenged 5 to 28 days after the initial injection, severe inflammation developed at the site of challenge within 12 to 24 hours. This secondary hypersensitive response was elicited by a dose of vaccine which produced little or no initial or delayed inflammation in a normal rat. Specific cutaneous hypersensitivity to a particulate antigen (i.e. typhoid vaccine) or a soluble antigen (human or rabbit gamma globulin) developed when rats were injected with a mixture of the antigen and pertussis vaccine. Pertussis vaccine mixed with typhoid vaccine did not enhance circulating agglutinin formation to typhoid vaccine. Cutaneous hypersensitivity to pertussis vaccine was passively transferred to normal rats by lymph node cells but not with serum from hypersensitive rats. Sensitization with pertussis vaccine did not enhance the edema-producing activity of histamine, serotonin, or 48/80 given subcutaneously. Mast cells in areas of hypersensitive inflammation were not damaged appreciably. The hypersensitive inflammation was not inhibited by treatment with anti-serotonin and antihistaminic drugs. Hypersensitive rats "depleted of mast cells" responded to challenge with pertussis vaccine with severe inflammation though their response to 48/80 was depressed. Hypersensitive rats treated with x-irradiation showed decreased hypersensitive inflammation though they responded normally to 48/80 and histamine. These studies failed to demonstrate a role for circulating antibody in the cutaneous hypersensitive inflammation produced in the rat by pertussis vaccine. Furthermore, the findings indicated that the cutaneous hypersensitive inflammation is not mediated by tissue serotonin and/or histamine.     

PRODUCTION OF HEMORRHAGIC NECROTIC SKIN LESIONS IN THE RABBIT BY MEANS OF HEMOPHILUS INFLUENZAE AND HEMOPHILUS PERTUSSIS

1. The intradermal injection of H. influenzae in the abdominal wall of rabbits induces inflammation, frequently combined with a central pustule. The corresponding injection of H. pertussis causes a bluish violet discoloration of the skin area involved which undergoes slight hemorrhagic necrotic changes within a few days. 2. The intravenous injection of living H. influenzae, 24 hours after the intradermal inoculation with living H. influenzae, is able to transform the respective skin areas into severe hemorrhagic necrotic lesions within 3 to 5 hours. 3. Heat-killed H. influenzae, if injected intravenously, may produce hemorrhagic-necrotic lesions in areas previously prepared with living or heat-killed H. influenzae. 4. H. pertussis, if injected intravenously, may cause, perhaps to a lesser extent, hemorrhagic necrotic lesions in skin areas 24 hours previously injected with H. influenzae. 5. The normal course of the infection of rabbit skin with H. pertussis is not, or not essentially, influenced by intravenous reinjection of living or killed H. influenzae or H. pertussis. 6. The agar washing filtrate of B. typhosus, if injected intravenously, can produce hemorrhagic necrotic lesions in rabbit skin prepared intracutaneously with living as well as with heat-killed H. influenzae. The intravenous injection of B. typhosus agar washing filtrate has no influence on areas prepared with H. pertussis. 7. Conversely, H. influenzae as well as H. pertussis, if injected intravenously, are able to produce hemorrhagic necrotic lesions in rabbit skin prepared 24 hours previously with B. typhosus agar washing filtrate. 8. The effectiveness of suspensions of H. influenzae apparently is confined to the bacteria themselves rather than to the supernatant fluids. This does not exclude the possibility of producing effective exotoxins under special experimental conditions.     

STUDIES ON VITAL STAINING : III. THE SIMULTANEOUS INGESTION OF TWO DYESTUFFS BY PHAGOCYTES. THE QUESTION OF "BLOCKADE OF THE RETICULO-ENDOTHELIAL SYSTEM"

When large amounts of brilliant vital red are injected into the blood stream of dogs, the dye is gradually removed from circulation, and most of it is deposited in numerous phagocytic cells which are scattered throughout various organs and tissues. The dye occurs largely in the form of tiny red granules crowded together in the cytoplasm of these cells. If Niagara sky blue, a closely related dyestuff, is injected, it too is taken up and stored in these same cells. It is shown that the presence of red dye in the tissues does not inhibit the cells from taking up the blue one. The normal ability of the phagocytes to take up Niagara sky blue is observed also when this dye is injected simultaneously with brilliant vital red. This normal response toward the blue dye is seen even though the phagocytes are busied at the same time in the process of engulfing and storing the red dye. These experiments show that it is difficult if not impossible to "block" the cells with one dye so that their ability to take up another is even slightly impaired. The two dyes employed in these studies are shown to be particularly suitable for experiments of the sort here reported.     

THE STATE OF THE VESSELS OF THE MESENTERY IN SHOCK PRODUCED BY CONSTRICTING THE LIMBS AND THE BEHAVIOR OF THE VESSELS FOLLOWING HEMORRHAGE

1. Direct observations of the arteries, arterioles, capillaries, veins, and lymphatics in the mesentery of anesthetized cats put into shock by incomplete occlusion of the circulation of the limbs showed that: (a) Marked constriction of the arteries and arterioles, produced by muscular contraction, occurred usually within an hour after incomplete occlusion of the limbs, lasted several hours, and finally gave way in most instances to relaxation an hour or more before death. The constriction reduced the blood supply to the mesentery and intestine and the venous return from them. It did not, however, interrupt the blood flow. No pooling or stagnation of blood was seen even as a terminal phenomenon. (b) The veins of the mesentery also became constricted but showed less tendency to dilate as death approached. The lymphatics likewise became somewhat narrowed. Even during the terminal stage the leukocytes moved along without change in shape or sticking to the walls of the capillaries or venules. (c) Hematocrit determinations showed progressive hemoconcentration of moderate degree. (d) Autopsy usually showed the presence of small hemorrhages in many parts of the body, especially the heart, liver, spleen, and lungs. (e) Bilateral nephrectomy, suprarenalectomy, and pancreatectomy did not significantly alter the morphological picture elicited by shock induced by restriction of the circulation to the limbs. 2. Removal of large amounts of blood was always followed within a short time by constriction of arteries, arterioles, veins, and lymphatics of the mesentery. 3. Fall in arterial pressure produced by pithing was not accompanied by change in diameter of the arteries, arterioles, veins, or lymphatics, or by blanching of the mesentery or gut.     

THE MANNER OF REMOVAL OF PROTEINS FROM NORMAL JOINTS

1. Data are presented showing that precipitin tests can be used for the detection of the proteins contained in egg white and horse serum in the blood stream and thoracic duct lymph following injection into the knee joints of normal dogs. The sera of rabbits immunized against the particular protein employed were used in doing the precipitin tests. 2. Egg white is removed only by way of the lymphatics, appearing more rapidly if the leg muscles are massaged. The removal is even greater from passively exercised joints. 3. Horse serum albumin is readily removed from a normal dog''s knee joint by way of the lymphatics alone and with greater rapidity from a passively exercised joint. Horse serum globulin escapes from normal joints with great difficulty, if at all, and therefore does not readily gain entrance into the underlying lymphatic capillaries. 4. The molecular size of a protein readily gaining egress from a joint through the lymphatics is thus defined. 5. The relative sizes of the albumin and globulin molecules contained in horse serum are confirmed by in vivo experiments. 6. The lymphatic system is the essential apparatus for the removal of protein from joints, and any interference with this drainage should promote the formation of intraarticular effusion. The data presented suggest that a simple clinical test for determining the efficiency of the lymphatics draining a single joint can be devised.     

INFECTIOUS FIBROMA OF RABBITS : IV. THE INFECTION WITH VIRUS MYXOMATOSUM OF RABBITS RECOVERED FROM FIBROMA

The serial passage of Virus myxomatosum through fibroma-recovered domestic rabbits did not alter its pathogenic properties. Fully virulent Virus myxomatosumpersisted in the inoculated testicle of fibromarecovered rabbits for at least 16 days following inoculation. Virus injected into the testicles of myxoma-immune domestic rabbits, on the other hand, was promptly rendered non-demonstrable. The failure of fibroma-recovered domestic rabbits to destroy injected Virus myxomatosumand the absence from their sera of neutralizing antibodies effective against Virus myxomatosum are considered to be evidence against the identity of the fibroma and myxoma viruses. The rapidity with which fibroma-recovered rabbits develop neutralizing antibodies following infection with Virus myxomatosum is considered to be a possible factor in their acquired resistance. It is believed on the basis of all the evidence that infectious fibroma of rabbits is a definite disease entity and not merely a mild and nonfatal form of infectious myxoma.     

Plasmonic colloidal pastes for surface-enhanced Raman spectroscopy (SERS) of historical felt-tip pens

Surface-enhanced Raman spectroscopy (SERS) has been identified as a suitable technique for the analysis of colorants in works of art. Herein, the application of SERS to the identification of dye compositions in historical felt-tip pens is reported, which is of paramount importance for the development of appropriate conservation protocols for historical drawings. In this study, three pens (pink, green, and blue colors) belonging to the film director Federico Fellini were analyzed. SERS measurements were performed directly on the pen lines drawn on a commercial paper by the deposition of Ag colloidal pastes, which allowed fast in situ dye identification without the need for extraction or hydrolysis treatments. Eosin Y was identified as the only dye present in the pink pen ink, whereas erioglaucine was found to be the main dye component in green and blue pen inks. SERS also resulted in highly efficient identification of the individual dyes erioglaucine, crystal violet, and rhodamine present as a mixture in the blue pen ink. The high SERS sensitivity was ascribed to the plasmonic effects and efficient quenching of the fluorescence interference of dyes. A comparison with contemporary pen inks highlighted minor differences in the chemical composition. These results prove that SERS can be used as a fast and sensitive analytical tool for ink analysis that provides invaluable support for the general assessment of the date, provenance, and originality of the historical drawings as well as for the development of preventive conservation protocols.

SERS analysis performed with silver nanopastes allowed in situ identification of dye compositions of the historical felt-tip pens used by Federico Fellini.     

ETIOLOGY OF OROYA FEVER : XIV. THE INSECT VECTORS OF CARRION'S DISEASE.

With a view to determining the mode of infection in Carrion''s disease, a study of the blood-sucking insects found in the districts of Peru where the disease prevails has been carried out, through the cooperation of The Rockefeller Institute and the Rockefeller Foundation. The material studied included ticks, mites, midges, lice, fleas, bedbugs, mosquitoes, buffalo gnats, horse-flies, "sheep ticks," 3 species of Streblidae, and 3 species of Phlebotomus, including Phlebotomus verrucarum Townsend and two new species which have been named Phlebotomus noguchii and Phlebotomus peruensis. The insects were collected without the use of chemicals, were prepared for transportation in such a manner as to prevent drying, and were shipped under conditions of refrigeration to New York, where they were inoculated into monkeys. The plan followed was to inject saline suspensions of the crushed insects intradermally into rhesus monkeys and to make cultures of the blood of the animals at intervals of 1 to 6 weeks after inoculation. The only class of insects in which the presence of Bartonella bacilliformis could be detected were phlebotomi. No cutaneous lesions were induced in monkeys injected with the crushed insects, but in the case of four different lots of phlebotomi the blood of the animals so injected yielded cultures of Bartonella bacilliformis which produced typical verrucous lesions on inoculation into other monkeys. The morphology and cultural characteristics of the Bartonella strains obtained from phlebotomi proved identical with those of strains isolated from human blood and skin lesions. Monkeys which had recovered from infection with the phlebotomus strains resisted inoculation with a human strain of Bartonella bacilliformis, and, conversely, monkeys which had passed through an infection induced by the human strain resisted inoculation with the strains obtained from phlebotomi. The experimental observations described in this paper lead us to conclude that certain phlebotomi act as insect vectors of Oroya fever and verruga peruana. The phlebotomi which have been shown quite certainly to carry the Bartonella bacilliformis are those of the species Phlebotomus noguchii. Phlebotomus verrucarum is also probably a vector, while Phlebotomus peruensis remains doubtful in this respect.     

STUDIES ON INFLAMMATION : II. A MEASURE OF THE PERMEABILITY OF CAPILLARIES IN AN INFLAMED AREA

1. By means of a colorimetric method the concentration of trypan blue in capillaries can be estimated by direct observation and its changes followed as the dye passes out of the circulating blood stream. 2. The change in concentration of trypan blue in the capillaries of both the normal and the inflamed mesentery of frogs can be described by two separate exponential equations of the type: y = be^-ax. 3. From these equations it is found that the rate of fall of concentration following intraventricular injection of the dye is almost twice as great in the capillaries of the inflamed as in those of the normal mesentery. This difference is a measure of increased permeability with inflammation.     

THE SKIN RESPONSE OF RABBITS TO NON-HEMOLYTIC STREPTOCOCCI : I. DESCRIPTION OF A SECONDARY REACTION OCCURRING LOCALLY AFTER INTRADERMAL INOCULATION.

1. Rabbits inoculated intradermally with certain strains of green streptococci have well marked lesions which, after reaching a maximum size in 24 to 48 hours and then beginning to retrogress, show in over 50 per cent of the animals a secondary increase in size and other signs of inflammation about 8 or 9 days after inoculation. 2. This secondary reaction may follow the inoculation of a variety of strains of green-producing streptococci from various sources, of indifferent streptococci, and occasionally of pneumococci. 3. The inoculation of hemolytic streptococci, staphylococci, Micrococcus catarrhalis, or Bacillus coli has not been followed by this secondary reaction. 4. The secondary reaction is not due to increased activity of the injected bacteria since the lesions are usually sterile at the time it occurs and since the secondary reaction occurs after inoculation of killed organisms as well as after that of living ones. 5. A second inoculation of green streptococci into a rabbit within 9 weeks of a first injection is followed by a primary but not by a secondary reaction. This inhibition of the secondary reaction is not specific; for the phenomenon of secondary reaction can be completely inhibited by previous inoculations of the rabbit with any living streptococcus and usually with pneumococci. Killed organisms are less effectual. 6. Preliminary injection with staphylococci, Micrococcus catarrhalis, and Bacillus coli has not prevented the appearance of a secondary reaction in response to subsequent injections of green streptococci. 7. The agent responsible for the secondary reaction has not as yet been determined; its nature is discussed. The phenomenon is possibly a form of allergic reaction.     

THE LYMPHATIC PARTICIPATION IN HUMAN CUTANEOUS PHENOMENA : A STUDY OF THE MINUTE LYMPHATICS OF THE LIVING SKIN

A technic is described for the demonstration of lymphatic capillaries in living skin and for their study. By means of vital dyes injected intradermally these vessels can be rendered plainly visible. They form an extraordinarily abundant anastomotic web. The least scratch, one which does not penetrate through the epidermis, gives rise to such conditions that lymphatic absorption readily takes place from the abraded surface; and so close-meshed is the lymphatic web that an intradermal injection with even the finest hypodermic needle tears some of the constituent vessels open with result that they undergo direct injection. In many individuals much of the fluid introduced at an ordinary intradermal injection, like that made in the clinic, spreads through the superficial lymphatic network, whereas in others it tends to enter the deeper lymphatics at once, the difference being due to merely physical factors determined by skin texture. Normal flow along the skin lymphatics is rapid even when the body is at rest, dye introduced into the skin of the resting forearm reaching the axilla within a few minutes. The observations make plain the fact that every intradermal injection is an intralymphatic one, often preponderantly such, while furthermore every local injection into the skin becomes within a few minutes a general one, so rapidly is the introduced material transported to the blood. The normal permeability of the skin lymphatics of man is approximately the same as that of the mouse. Tests indicate that in both instances the lymphatic wall behaves like a semipermeable membrane. The permeability of the human lymphatic wall like that of the mouse is subject to rapid and great changes. A stroke on the skin with a blunt instrument to produce a wheal, causes the lymphatic capillaries to become so permeable temporarily that dyes pass through their walls as if practically no barrier existed, instead of being held back for a greater or less period. Slight inflammation due to heat, ultraviolet light or bacterial products has a similar effect. So, too, has histamine. When fluid pours rapidly into the tissue from the blood, as when a wheal is formed, the lymphatics are compressed and their efficiency as drainage channels is interfered with. These facts are briefly discussed in their bearing upon skin phenomena in general. The lymphatics cannot be disregarded in considering such phenomena, in which it is plain that they have a large share.     

THE INFLUENCE OF URIC ACID ON THE PERMEABILITY OF MEMBRANES

1. Congo red injected in vivo together with uric acid gives rise to more intense and diffuse red coloring in rats, especially in the subcutaneous and peri-articular tissues, than is the case in control rats injected simply with dye. 2. Uric add added in vitro to solutions of Congo red or trypan blue increases the speed of diffusion of these dyes, both through gelatin and the animal membranes (dialyzers). These results support a view long maintained by Professor Rondoni (25), namely, that some factor of an endothelial-capillary nature must be taken into consideration in manifestations of hyperuricemia and of gout.     

CHANGES IN THE CUTANEOUS LYMPHATICS OF HUMAN BEINGS AND IN THE LYMPH FLOW UNDER NORMAL AND PATHOLOGICAL CONDITIONS

Vital dyes injected intradermally enter lymphatic capillaries directly, rendering them visible, and appear later in the draining lymphatic trunks as colored streamers. The method enables one to perceive the state of the lymphatic channels and the rate of lymph flow within them. It yields consistent results when tested under physiological conditions known to increase or decrease lymph flow. In the horizontally placed normal limb at rest there is slight lymph flow. In a normal leg or arm hanging downward lymph flow ceases although fluid in the limb increases. When a previously dependent arm is raised above the head, or when the foot of a seated subject is propped on a table, lymph flow in the raised limb becomes active. It ceases in the skin of an arm subjected to partial obstruction of the veins by pressure from without, but very active lymph flow appears during the reactive hyperemia which follows upon the release of venous obstruction. It is still greater following release of total circulatory obstruction, and seems to be the same whether or not the limb has previously been engorged with blood. In the ischemic patches which appear in the skin of a limb during total circulatory obstruction (Bier''s spots) the lymphatic capillaries are definitely and considerably constricted, whereas they are slightly dilated in the purple, congested regions of the skin round about. On release of obstruction there occurs a strikingly rapid, equal lymphatic drainage from both regions. The significance of all the findings is discussed. When dye is injected intradermally and the skin sucked, much of the foreign material is driven into the lymphatics draining the injected area.