Pathogenesis 471 



Monti* claimed to have found that a characteristic croupous pneu- 

 monia results from the injection of cultures into the trachea of sus- 

 ceptible animals. A very interesting review of the literature of the 

 experimental aspects of the subject, embracing 198 references, will 

 be found in Wadsworth's paper upon ' 'Experimental Studies on the 

 Etiology of Acute Pneumonitis." f 



The final proof that true pulmonary consolidation, i.e., pneumonia, 

 can be produced experimentally by cultures of the pneumococcus is 

 to be found in a paper by Lamar and Meltzer. % These investigators 

 etherized dogs, kept the mouth open by means of a large wooden 

 gag, drew the tongue forward by means of hemostatic forceps, 

 and then, seizing the median glosso-epiglottic fold, pulled it for- 

 ward so that the posterior aspect of the epiglottis presented an in- 

 clined plane. Into this concavity one end of a tube is placed. 

 Under the protection of the left index-finger the tube was directed 

 into the larynx and pushed down slowly and gently through the 

 trachea until a resistance was met with. The inner end of the tube 

 was then found to engage in a bronchus — usually the right bronchus. 

 A pipette containing a hquid culture of the pneumococcus was next 

 attached to the external end of the tube, and by means of a syringe 

 the culture (about 6 cc.) was injected into the bronchus. The 

 syringe was then removed, the piston withdrawn, and the syringe 

 again attached to the pipette. By the injection of air the culture 

 was driven deeper into the bronchi. The tube was then clamped and 

 withdrawn and the animal released. By these means experimental 

 pneumonia, with the typical consolidation and lobar distribution, 

 was produced in 42 successive cases. The course of the inflamma- 

 tory disturbance thus produced was rapid, and in one case nearly 

 complete consoUdation had occurred in seven hours. 



Lesions.' — The lesions of croupous pneumonia of man are almost 

 too well known to need description. The distribution of the disease 

 conforms more or less perfectly to the divisions of the lung into 

 lobes, one or more lobes being affected. An entire lung may be 

 affected, though, as a rule, the apex escapes consolidation and is 

 simply congested. The invaded portion of the lung is supposed to 

 pass through a succession of stages cUnically described as (i) con- 

 gestion, (2) red hepatization, (3) gray hepatization, and (4) resolu- 

 tion. In the first stage bloody serum is poured out into the air-cells, 

 filling them with a viscid reddish exudate. In the second stage this 

 coagulates so that the tissue becomes solid, airless, and approxi- 

 mately like liver tissue in appearance. The third stage is charac- 

 terized by dissolution of the erythrocytes and invasion of the diseased 

 air-cells by leukocytes, so that the color of the tissue changes from 

 red to gray. At the same time the coagulated exudate begins to 



* "^eitschrift fur Hygiene," etc., 1892, xi, 387. 

 t"Amer. Jour. Med. Sciences," 1904, cxxvn, p. 851. 

 % "Jour. Exp. Med.," 1912, XV, No. 2, p. 133. 



