STUDIES UPON EXPERIMENTAL PNEUMONIA IN RABBITS : V. THE R?LE OF THE LEUCOCYTE IN EXPERIMENTAL PNEUMONIA. THE RELATION OF THE NUMBER OF ORGANISMS INJECTED TO THE MORTALITY.

1. The importance of the leucocyte in the resistance of animals to experimental pneumonia is emphasized by the fact that animals treated with benzol, a leucotoxic substance, rapidly succumb to the disease, while animals treated in like manner with toluol, a very similar chemical substance causing no leucopenia, show no decreased resistance. 2. The rôle of the leucocyte in the resistance of animals to experimental pneumonia is further emphasized by the fact that animals that respond to the pneumococcus infection with a leucocytosis, as occurs after the repeated injection of toluol, are more resistant to the pneumonia. Further, the hyperleucocytosis produced by repeated injection of nutrose before the production of pneumonia likewise seems to increase the resistance of the animals. 3. Experimental pneumonia is not necessarily fatal in rabbits. The factors determining the outcome of the disease are numerous; among these is the number of bacteria inoculated. Animals receiving small doses usually survive, while those receiving comparatively large numbers usually succumb.     

THE R?LE OF THE RETICULO-ENDOTHELIAL SYSTEM IN IMMUNITY : I. THE R?LE OF THE RETICULO-ENDOTHELIAL SYSTEM IN THE PRODUCTION OF DIPHTHERIA ANTITOXIN.

1. Following massive doses of India ink injected intravenously into guinea pigs before a subcutaneous injection of diphtheria toxin-antitoxin mixture, no antitoxin was found in the blood serum for 3 weeks, as indicated by intracutaneous tests, whereas an appreciable amount could be detected in non-blocked, immunized control animals. 2. During the 4th week following immunization, the titer of the serum of blocked animals equaled that of non-blocked controls within the limits of the intracutaneous test dose. 3. The smaller doses of India ink used in these experiments, given before immunization, had no stimulating effect on the production of diphtheria antitoxin but, on the contrary, also inhibited the appearance of this antibody, although to a less extent.     

EXPERIMENTS ON THE R?LE OF LYMPHOID TISSUE IN THE RESISTANCE TO EXPERIMENTAL TUBERCULOSIS IN MICE

Mice either normal or splenectomized after exposure to X-ray are markedly more susceptible to bovine tuberculosis than are normal animals. Animals splenectomized a short time prior to inoculation are also more susceptible than normal, while those splenectomized eight to ten days before inoculation have about the same resistance as normal. The mice splenectomized three to four weeks before inoculation have a resistance increased over the normal, as has already been shown by Lewis and Margot. As X-ray in the doses used apparently affects only the lymphoid tissue and as the hypertrophy of the remaining lymphoid tissue after splenectomy is so rapid that the circulating lymphocytes may be much above the normal by the third week, it is concluded that this evidence, taken with the well known association of the lymphocytes with tuberculous lesions, points strongly to the lymphocyte as an important agent in the defensive mechanism against tuberculosis.     

EXPERIMENTS ON THE EPIDEMIOLOGY OF PSEUDORABIES : I. MODE OF TRANSMISSION OF THE DISEASE IN SWINE AND THEIR POSSIBLE R?LE IN ITS SPREAD TO CATTLE

Pseudorabies is a very fatal but non-contagious disease in cattle and the common laboratory animals. It is a relatively mild yet highly contagious disease in swine. It has been shown that in swine the nose serves both for the entrance and the exit of the virus. Furthermore, it has been observed that fatal pseudorabies infections in rabbits can be induced merely by bringing their abraded skin into contact with the noses of infected swine. The blood sera of swine on two farms where pseudorabies had occurred among the cattle were found to be capable of neutralizing pseudorabies virus. It is believed that in these instances the swine had a mild and unrecognized pseudorabies infection and transmitted their disease to the cattle with which they were associated, by transfer of the virus on their noses to the abraded skin of the cattle.     

THE RELATION BETWEEN ANTIANAPHYLAXIS AND ANTIBODY BALANCE : I. THE R?LE OF EXCESS OF CIRCULATING ANTIBODY IN HYPERSENSITIVENESS

1. Sensitized guinea pigs injected with normal rabbit or guinea pig serum previous to intravenous inoculation of antigen may be protected against a few lethal doses of antigen. The protection is greater with foreign than with homologous serum and appears to be related roughly to the amount of serum introduced. 2. Sensitized guinea pigs injected with antibody-containing serum preliminary to intravenous injection of antigen, show no greater refractoriness to anaphylaxis than do those injected with normal serum. 3. Moreover, in many instances, the injection of an excess of antibody into the circulation of sensitized guinea pigs, leads to an increased susceptibility of these animals to anaphylaxis. 4. These results indicate that an excess of circulating antibody is not responsible for a state of antianaphylaxis, but on the contrary, may contribute toward the anaphylactic reaction itself.     

EXPERIMENTS ON THE R?LE OF LYMPHOID TISSUE IN THE RESISTANCE TO EXPERIMENTAL TUBERCULOSIS IN MICE : III. EFFECT OF HEAT ON RESISTANCE TO TUBERCULOSIS.

Mice with high lymphocyte counts and increased activity of the lymphoid tissue induced by one exposure to intense dry heat exhibit a marked increase in the resistance to large doses of bovine tubercle bacilli as compared with that shown by control animals given a similar inoculation. This resistance, judged by the time of survival after inoculation, is increased from two- to threefold. The average length of life after inoculation for three groups of heated mice was 88, 69, and 67 days respectively, while the control groups averaged 16, 29, and 28 days respectively.     

EXPERIMENTS ON THE R?LE OF LYMPHOID TISSUE IN THE RESISTANCE TO EXPERIMENTAL TUBERCULOSIS IN MICE : II. EFFECT OF CANCER IMMUNITY ON RESISTANCE TO TUBERCULOSIS.

Mice so x-rayed as greatly to reduce the lymphoid tissue are rendered highly susceptible to tuberculous infection. On the other hand) when a marked lymphocytosis is induced by first immunizing mice against, and then inoculating them with cancer, the resistance to tuberculous infection is greatly enhanced. This heightened resistance may be set aside and even changed to a state of increased susceptibility to the infection by again depleting the lymphocytes by means of the x-ray.     

THE RóLE OF STREPTOCOCCI IN EXPERIMENTAL POLIOMYELITIS OF THE MONKEY

It is the opinion of Bull, that the streptococci recovered from poliomyelitic tissues, while having no etiological or pathological relationship to the virus of poliomyelitis, occur as secondary invaders in the disease. Smillie and Amoss indicated that the bacteria may be agonal invaders. The results of the experiments reported in this paper point to another source of the streptococci. They occur as contaminants which are introduced into the cultures during the process of grinding tissues. The source of the streptococcus may therefore be the air of the place in which the cultures are made. We have come to this conclusion because first, the tissues of which cultures yielded streptococci were derived from a number of monkeys with experimental poliomyelitis still in a vigorous state. Secondly, when the tissues were ground bacteria were noted much more frequently in their cultures than in those in which fragments of the same brains were used. Thirdly, microorganisms occurred more often in cultures made in the routine laboratory than in a special room where asepsis was carried to the extreme of a major surgical operation on man. Fourthly, streptococci were obtained from the air of the places where cultures were made. Finally, there is no correlation between the cultures of two portions of the same brain. The streptococci occurred in some cultures in pure growth and in others admixed with other ordinary species of bacteria. The latter were often found, in turn, in pure culture and what applies to streptococci, as mentioned in the preceding paragraph, applies equally to the staphylococci, diphtheroids, spore-bearing rods, and other miscellaneous, familiar microorganisms. We could not determine that there exists any etiological relation of the streptococci to poliomyelitis. The fermentation reactions of the microorganisms obtained from the air, from non-poliomyelitic and poliomyelitic monkey brains indicate that bacteria from any of these sources are markedly different. So also with the serological reactions of agglutination and precipitation. Furthermore no agglutination was observed when the serum of monkeys convalescent from experimental poliomyelitis was mixed with any of the streptococci recovered or those received directly or indirectly from Rosenow. Moreover, the intracerebral injection with cultures, irrespective of their source, induced in rabbits a purulent type of meningoencephalitis, often associated with streptococcic septicemia. This result is at marked variance with any known effects of the true filtrable virus of poliomyelitis in man and in the monkey.     

THE R?LE OF THE LYMPHOCYTE IN ANTIBODY FORMATION

Following the injection of typhoid antigen or sheep erythrocytes into the pad of the rabbit''s hind foot, lymph from the efferent lymphatic of the popliteal lymph node was collected and analyzed for antibody content. On separating the lymphocytes from the lymph plasma, it was found that the antibody titer of the cell extract was substantially and consistently higher than that of the surrounding fluid. This difference was greatest at the time of greatest rate of increase of antibody titer in the whole lymph, rather than when the antibody titer of the lymph plasma was highest. These results can only be interpreted to mean that the lymphocytes either produce antibodies or take them up from the lymph plasma. Incubation in vitro of lymphocytes containing one species of antibody with lymph plasma containing another showed that antibodies pass from the cells to the supernatant lymph fluid to reach approximate equilibrium; acquisition of antibody from supernatant lymph fluid was not observed. Similar results were obtained when normal lymphocytes were allowed to incubate in vivo in their own lymph fluid to which antibodies had been added. It was again found that antibodies were not absorbed or adsorbed by lymphocytes. These results seem to indicate that lymphocytes are instrumental in the formation of antibodies.     

SOME OBSERVATIONS ON THE LYMPH AND BLOOD VESSELS OF THE RABBIT TRACHEA : WITH PARTICULAR REFERENCE TO THEIR R?LE IN THE PATHOGENESIS OF EXPERIMENTAL LOBAR PNEUMONIA.

1. Winternitz, Smith, and Robinson have offered as experimental evidence in support of the lymphatic path of infection in lobar pneumonia, a series of injection experiments of the rabbit''s tracheal submucosa. What these investigators supposed to be lymphatics are shown by us to be an unusual type of venous supply consisting of short, wide, and richly anastomosing vascular channels. 2. There is little homology between the structure and distribution of the lymph and blood vessels in the human and rabbit trachea. 3. Injections of pneumococci by the tracheal route to produce lobar pneumonia in the rabbit include an intravenous administration of these organisms when the mucosa is pierced or injured.     

THE R?LE OF THE THEBESIAN VESSELS IN THE CIRCULATION OF THE HEART

In summary, evidence has been presented to show a direct connection other than through the capillaries between the coronary arteries and the chambers of the heart. This connection was shown by perfusion, injections and serial sections to be through the Thebesian veins. Communications between the larger coronary veins and the Thebesian veins were also demonstrated by the same methods. Serial sections through Thebesian veins have shown capillaries draining directly into them. Under certain conditions it has been shown that as much as 90 per cent of the arterial flow may escape via the Thebesian vessels. Lastly, in the event of gradual closure of the orifices of the coronary arteries, the Thebesian vessels can supply the heart muscle with sufficient blood to enable it to maintain an efficient circulation.     

THE R?LE OF THE RETICULO-ENDOTHELIAL SYSTEM IN IMMUNITY : III. THE PRODUCTION OF ACTIVE AND PASSIVE ANAPHYLAXIS IN THE BLOCKED ANIMAL.

1. Guinea pigs injected intravenously with massive doses of India ink before active sensitization exhibited occasionally a more or less marked, decreased sensitiveness to the reinjection of the antigen. 2. The serum of rabbits which had received massive doses of India ink before the sensitizing injections, showed approximately the same titer of anaphylactic antibodies as that of sensitized normal control animals, as demonstrated by the degree of passive sensitization induced in guinea pigs. 3. The precipitin titer of sensitized rabbits blocked with massive doses of India ink was somewhat lower than that of sensitized normal controls. In one instance, the intravenous injection of smaller doses of India ink was followed by a higher precipitin titer. No uniform relation was found between the height of the precipitin titer and the anaphylactic power of the antiserums. 4. One blocking injection of India ink given to guinea pigs before passive sensitization did not interfere with the occurrence of anaphylactic shock nor alter its nature.     

STUDIES ON THE MECHANISM OF RECOVERY IN PNEUMONIA DUE TO FRIEDL?DER'S BACILLUS : III. THE R?LE OF "SURFACE PHAGOCYTOSIS" IN THE DESTRUCTION OF THE MICROORGANISMS IN THE LUNG

Phagocytosis of encapsulated Friedländer''s bacilli has been demonstrated in the lungs of rats in the absence of both circulating and local antibody. The mechanism of phagocytosis independent of antibody has been shown to be due to the same surface factors that operate in the phagocytosis of Type I pneumococcus under similar conditions. Direct observation of the phagocytic process reveals that leucocytes in the lung can phagocyte unopsonized Friedländer''s bacilli only by trapping them against the surfaces of alveolar walls or bronchi, or by pinning them against the surfaces of adjacent leucocytes. Evidence is presented that Friedländer''s bacilli thus phagocyted are rapidly killed in the cytoplasm of the phagocytic cells. Reasons are discussed for the failure of prolonged chemotherapy to cure lung abscesses that not infrequently complicate the pneumonia due to Friedländer''s bacillus.     

THE R?LE OF THE THYROID IN THE REGULATION OF THE BLOOD CHOLESTEROL OF RABBITS

1. The blood cholesterol of rabbits on a normal diet without added cholesterol is increased only slightly (19 per cent) by thyroidectomy. 2. In rabbits with a hypercholesterolemia due to long continued cholesterol feeding, thyroidectomy causes a marked rise (137 per cent) in the blood cholesterol. This rise is usually maintained. 3. When long continued cholesterol feeding has failed to cause a rise in the blood cholesterol of rabbits, thyroidectomy abolishes this resistance and a hypercholesterolemia is promptly produced. 4. A single injection of thyroxin causes a significant drop in the blood cholesterol of rabbits with hypercholesterolemia. This reaction is not influenced by thyroidectomy. 5. Potassium iodide causes an increase in the blood cholesterol of rabbits with hypercholesterolemia. This reaction is not influenced by thyroidectomy in contrast to the effect of KI in preventing a rise in blood cholesterol when given concurrently from the beginning of cholesterol feeding, an effect which is abolished by thyroidectomy. It is suggested that two different mechanisms are involved. 6. A single injection of insulin produces a fall in the blood cholesterol of rabbits with hypercholesterolemia. If anything, thyroidectomy increases the magnitude of this effect.     

THE R?LE OF THE RETICULO-ENDOTHELIAL SYSTEM IN IMMUNITY : V. PHENOMENA OF PASSIVE IMMUNITY IN BLOCKED AND SPLENECTOMIZED MICE.

1. Blockade of the reticulo-endothelial system by means of one intravenous injection of India ink as well as splenectomy did not alter the course of either Pneumococcus Type I infection or tetanus intoxication in mice. 2. The protective action of Antipneumococcus Type I serum against the corresponding infection, as determined by the injection of in vitro prepared mixtures of serum and culture, was definitely lower in mice which had received one blocking injection of India ink shortly before the test. 3. Titration of tetanus toxin and antitoxin in blocked and splenectomized mice gave results identical with those obtained in normal mice, if in vitro prepared and incubated toxin-antitoxin mixtures were injected. The degree of protection, however, conferred by a preceding dose of antitoxin against subsequent intoxication, was markedly lower in blocked mice than in normal control animals, this difference becoming more pronounced with the increase of the time interval.     

THE R?LE OF THE SOLUBLE SPECIFIC SUBSTANCE IN ORAL IMMUNIZATION AGAINST PNEUMOCOCCUS TYPE I

1. Feeding the purified soluble specific substance of Type I pneumococcus protects rats against an intraperitoneal injection of the virulent organism. 2. This increased resistance resembles that obtained when the intact (dead) or dissolved bacteria are fed, as follows: (a) one feeding is sufficient, (b) the interval between the feeding and the appearance of the immunity is the same, (c) the duration is approximately the same, (d) when the immunity is exhausted it can be renewed by a new feeding, (e) the immunizing action is type-specific. 3. The differences between the effects of feeding the purified specific substance and the intact or dissolved organism to rats, appear to be quantitative rather than qualitative, the proportion of animals protected and the height of the immunity being generally, though not always, less in the case of the former. 4. In contrast to the immunizing action which the soluble specific substance possesses when administered to rats, feeding it to mice failed to protect them. Neither were mice definitely immunized by parenteral administration. 5. A sodium glycocholate solution of Pneumococcus Type I lost part of its immunizing activity on standing for 1 year. 6. The failure to immunize mice and the loss of activity of the bile salt solution of pneumococcus, on standing, are discussed in terms of (a) the possible presence of a second cell constituent which is active by mouth, and (b) a possible intramolecular change in the type-specific polysaccharide associated with a loss of immunizing action while retaining the precipitin reaction.     

STUDIES ON THE MECHANISM OF RECOVERY IN PNEUMONIA DUE TO FRIEDL?NDER'S BACILLUS : I. THE PATHOGENESIS OF EXPERIMENTAL FRIEDL?NDER'S BACILLUS PNEUMONIA

Experimental pneumonia due to Friedländer''s bacillus was produced in white rats by the intrabronchial inoculation of the bacilli suspended in mucin. The pneumonia was lobar in type, was almost uniformly fatal, and simulated the acute form of the natural disease in human beings. The pathogenesis of the pneumonic lesion was studied by examination of microscopic sections of the lungs of animals killed at frequent intervals during the course of the infection. The histologic characteristics of the various stages of the pneumonia were essentially the same as those previously described in experimental pneumococcal (Type I) pneumonia except for the following differences: (1) In isolated areas of the lung in Friedländer''s pneumonia many more bacteria were encountered in the alveoli than were ever noted in experimental pneumococcal pneumonia. (2) Abscess formation was common in the late stages of Friedländer''s infection, whereas it was not noted in the pneumococcal lesion. (3) Organization of the alveolar exudate, rarely observed in experimental pneumococcal pneumonia, was a prominent feature of the pneumonia due to Friedländer''s bacillus. The mechanism of spread of Friedländer''s lesion appeared to be the same as that of pneumococcal pneumonia. Likewise there was noted the same phagocytosis of organisms in the lungs of even bacteremic animals dying of the infection.     

THE R?LE OF THE RETICULO-ENDOTHELIAL SYSTEM IN IMMUNITY : VI. THE EFFECT OF ENDOTHELIAL BLOCKADE ON THE STORAGE AND DISTRIBUTION OF NEOARSPHENAMINE

1. Blockade of the reticulo-endothelial system by means of a single injection of India ink caused a marked retention of neoarsphenamine in the blood of guinea pigs during the first twenty minutes of observation after intravenous injection, as contrasted with the rapid disappearance of the drug from the blood of normal controls. 2. Rabbits blocked by a single dose of India ink showed a slower elimination of the drug from the circulation following the first few hours after intravenous injection than corresponding controls. 3. The arsenic content of the liver of mice, which received neoarsphenamine intravenously after a preceding blocking injection with India ink, was appreciably lower than the arsenic content of the normal organ under similar experimental conditions.