PART I.: EXPERIMENTAL PNEUMONIA

RESUMÉ.In the foregoing we have shown that several investigators have succeeded in porducing experimental pneumonia in defferent kinds of animals — including those which are especially susceptible — by inroducing pneumococcus‐cultures inot the air‐passages (trachea). On the basis thereof we have adopted that mode of procdure in order to produce pneu monic infiltration in rabbits.For introduction of the bacteria‐cultures we have sometimes employed puncture of the trachea, sometimes intubation through the larynx. By these methods 52 rabbits have been infected. In the case of 4 of them no illnes developed. In 4 animals there occurred a slight rise of temprature, while at the same time on phkysical examination of the lungs there were detected bronchitic sounds or faint bronchial breathing. These rabbits recovered completely. Three of the animals got simple broncho‐pneumonia, while 2 rabbits displayed broncho‐pneumonic nodes together with however was not very extensive or well‐developed. In 17 of the animals the pneumonia was of considerable extension and fully developed. Furthermore there occured in 5 extension and fully developed. Furthermore there occurred in 5 rabbits an extremely well‐developed and diffused pneumonic infiltratio with a very acute and violent clinical picture. IN 3 of the experiments the illness proceeded mainly as a pneumococcus‐sepsis. On dissection the lungs were found to be hyperaemic, somewhat oedematous, but not infiltrated. In these cases the animals died before the pulmonary infiltration had come to development.In 4 rabbits the result of the infection was entirely divergent from the others. In one case there developed in the course of 2 months a chronic pulmonary infiltration with empyema pleurae, while in another animal there arose no process from the respiratory organs, whereas ther were signs of meningitis and myelitis.In 2 of the animals, into which the cultures had been introduced by puncture of the trachea, ther was found phlegmon in the connective tissue around the windpipe, as well as a retrosternal abscess cavity.With respect to the clinical picture of the pnenmonia the following points may be mentioned. The general condition of the animal rapidly becomes impaired. The appetite decreases. Under the development of the dissease the general condition becomes to some extent worse, but a pronounced deterioration is a rule not observed until a few hours before death.The body‐temperature in those animals in which pneumonia develops from 6 to 8 hours after infection rises rapidly up to 40° —41° and remains at that point during the illness with more or less fluctuation. In the animals that recovered the temperature fell again in the course of a couple of days. The rabbits which died of pneumonia showed as a rule a moderate decrease in the course of the last 24 hours or else a very pronounced collapse‐temperature.The frequency of respiration is in most cases slower and deeper than is usual in rabbits. There is lively action of the nostrils.The respiratory sound becomes as a rule in the course of 15–48 hours after infection pneumonic bronchial. There occur bronchitic sounds, as well as fine and coarse crepitations.The pulse‐frequency is not materially increased.On pathological‐anatomical examination the principal discoveries made were as follows.The lungs. The pneumonic process showed all transition stages from simple broncho‐pneumonia to compact lobar infiltration with fibrinous exudation. In the last‐named case the inflammation regularly resembled human pneumonia in the red hepatisation stage. Only in one single case was there observed gray hepatisation with partial transition to abscess.The pneumonic process proceeded as a rule from those parts which lie nearest to the root of th lung. These portions were the first to be infiltrated, and, where the inflammation extended to the whole lobe, the pneumonia was usually here most highly developed.In the most acute infections there were generally found hemorrhages in the lung‐tissue, while those parts of the lungs which were not attacked showed distinct vicarious emphysema. In some rabbits that died with the clinical picture of sepsis the infiltration was inconsiderable. The lungs were highly hyperasmic, showed hemorrhages, general emphysema and oedema.The pleura. A thin coating of fibrin on the pleurae viscerales was frequently seen, but pronounced fibrinous pleurisy was found only in two rabbits. In one animal ther was found typical fibrino‐purulent polyserositis.The heart. The endocardium and the valves of the heart were normal in all the animals dissected. In some of the hearts examined the muscles were flaccid and the heart delated, especially the right half. This phenomenon was rarely found in the rabbits in which the pneumonia might be bescribed as mild, whereas it was present in half the number of animals that had diffused and well‐developed pneumonia and in all the rabbits with the most violent and acute infections.Pericarditis was found only in th above‐mentioned case where there was polyserositis, as well as in a rabbit which showed gray hepatisation together with abscess‐formation.The liver, spleen and kidneys appeared on macroscopic examination to be normal in most of the experiments. In some of the most violent infections the liver was degenerated.The spleen was found only in a single case decidedly swollen and soft, whilst ther was also in one rabbit observed degeneration of the kidneys.