137 



'The thickness usually varies from 0-5 mm. to 4 mm. ; 6 mm. to 

 8 mm. is, however, no rarity. The subjacent pulmonary tissue is always 

 oedematous and atelectatic. 



The pleura costalis was only in one case attached to the pleura 

 pulmonalis by fibres. The pleura diaphragmatica is only very rarely 

 attached in a similar manner to the diaphragm. The spongy tissue of 

 the fibrinous deposit is completely filled with a sero-yellowish fluid. The 

 pleural cavity itself is filled with a reddish-yellow serum, containing 

 scattered flakes of fibrine. This fluid, the virus par excellence, coagulates 

 fairly readily when in contact with the atmosphere, but expresses a large 

 quantity of serous liquid. On removing the fibrinous deposit, the pleura 

 appears as a miich thickened, opaque, whitish membrane, which gradually 

 merges into the diffuse grey pleura of the whole lung ; these discoloura- 

 tions are often pigmented, and streaked with small rarely ramificated 

 blood vessels. Wherever the septum mediastinale is preserved, one finds 

 yellow gelatinous masses, which separate the cava pleuralia in the form 

 of tumoiirs. On incision a considerable quantity of fluid escapes. In 

 two cases the oesophagus was deflected by infiltration of solid masses of 

 fibrine, the exudative process having here also affected that organ. As 

 a consequence, a pericarditis fibrinosa per contiguitatem had arisen. 



The changes are Yerj varied in the cases under review. Frequently 

 only small reticulations of fibrine and capillary ektasia are present, giving 

 the pleura the appearance of a simple pleuritis sicca. This can be con- 

 sidered to be, from the point of view of comparative anatomy, the secondary 

 consequence of the subjacent croupous pneumonia. Through Nocard's 

 researches it was demonstrated that the affection of the interstitial tissue 

 is primary, and that the fibrinous pleuritis arises secondarily per con- 

 tinuitatem. It is therefore clear that when the fibrinous exudation has 

 reached the great extent it does, and the serous exudate has become 

 prominent, the process of the disease has already reached an advanced 

 stage. I paid special attention to the question if the portions adjacent 

 to the pleura showed an older stage of pneumonia than the pleura itself ; 

 this could be demonstrated to be the case in 80 per cent, of the cases. 

 I cannot go into the question here, why the interstitial tissue of the 

 lungs or its lymphatic vessels must be the points of attack of the pleuro- 

 pneumonia virus, as has been demonstrated experimentally and com- 

 paratively. As shall be shown further on, the pleura behaves in just the 

 same manner towards the virus of pleuro-pneumonia, on account of its 

 wealth of lymphatics, as do the serous membranes generally. 



The morbid portion of the lungs is conspicuous on account of its great 

 roundness and tougher consistence , it is consequently very easy to 

 separate the diseased tumescent portions from the normally collapsed 

 tissues of the healthy parts. The diseased lobes attain dimensions such 

 as are otherwise never observed. The condition of the lungs remind me 



