CATARRHAL PNEUMONIA. 195 



as a rule, throughout an entire lobe of a lung, or at least throughout a 

 large portion of a lobe, catarrhal pneumonia almost always remains 

 limited to single lobuli, and hence has also obtained the names of 

 lobular, disseminated, insular pneumonia, in contradistinction to the 

 lobar or croupous pneumonia. 



If the process have developed in the midst of pulmonary tissue 

 which contains air, we observe in the affected lung distinct scattered firm 

 points corresponding to the inflamed lobuli, which lie chiefly upon the 

 periphery of the lung, and are then distinctly wedge-shaped. Their 

 surfaces lie upon a level with that of the surrounding parts. At first 

 they are of a bluish red ; later, if the transudation and cell-growth 

 predominate, they have a lighter and more grayish color. Upon sec- 

 tion, the surface presents a smooth homogeneous appearance, and 

 there are none of the granulations characteristic of croupous pneumo- 

 nia. Upon lateral pressure upon the inflamed spot, there flows over 

 the cut surface an opaque liquid, at first bloody, and afterward pale-gray 

 in color, in which, under the microscope, we may see numerous cells, 

 some of them already in a state of fatty metamorphosis. In a more 

 advanced stage, these inflammatory centres undergo the same changes 

 which we have described as taking place in the spots enclosed in col- 

 lapsed pulmonary tissue. The gradual transition of atelectasis into 

 catarrhal pneumonia has recently been studied and described with 

 accuracy by Bartels and Ziemssen. These observers agree in rep- 

 resenting that the collapsed portions of lung exhibit alteration of 

 structure even when the collapse is quite recent. In slighter cases, 

 this alteration is limited to the lower sharp edge of the lungs, and to 

 a vertical stripe about two inches wide at their posterior edge upon 

 either side. In severer and more protracted cases, the entire lower 

 lobes of each side are involved, the process sometimes extending as 

 far as the back and inner side of the upper lobes. An attempt to 

 inflate them will succeed; but an unusual amount of force is requisite 

 for the purpose ; and the reinflated portion does not resume its former 

 pink color, but becomes of a deep scarlet or vermilion red, a proof 

 that the blood in it has increased considerably in quantity. When 

 the collapse is of long standing, the collapsed parts become more vo- 

 luminous and resistant, and we find in them separate compact knots of 

 irregular form and size. If we now inflate the lung, these knots 

 remain unchanged while the surrounding parts expand and fill with 

 air. Upon section we constantly find in the centre of these spots a 

 dilated bronchiole filled with tenacious secretion. The cut surface 

 resembles that of the spots of catarrhal inflammation in the uncollapsed 

 *iing-substance (see above). In a more advanced stage, the numer- 

 ous small centres of infiltration often coalesce into voluminous massop 



