in the walls of the vessels is very rare. The elastic tissues of the intima 

 and media are interrupted by the necrotic elements. Direct dissolution 

 of the media was observed in vessels near to large necrotic portions of 

 the lungs, here nucleated flaky masses, in which remains of elastic elements 

 stain faintly, are seen. In later stages these rudiments are replaced by 

 elements of connective tissue. 



Reviewing the above, we find that an arteriitis as described by Csokor 

 is really present, but the arteriitis is due in the first place to the lymphan- 

 gitis, as is seen from the lesions in the adventitia and media. Cfhe disease 

 is restricted to these two layers and spreads along the course of the lymph 

 spaces of the vessels, demonstrating the inflammation per continuitateni. 

 It may be that the pleuro-pneumonia virus acts primarily, or it may be 

 that small embolic infarcts in the lymph spaces of the walls of the capillaries 

 and blood vessels incite the described regressive processes. 



The Pleura. 



I intend to point out in short the changes which take place directly 

 in or underneath the intermediate zone of fibrine and pleural tissue. The 

 fibrine itself usually lies in small pitlike depressions, from which its fila- 

 ments grow outwards in great quantities, covering eventually the whole 

 of the pleura. In the zone between fibrine and pleura, one sometimes 

 find a epithelial layer with large nuclei, of this occasionally only the 

 detritus remains. The epithelial layer becomes more and more destroyed 

 as the pneumonic process spreads further over the pleura. 



But we usually have to do with old pleuritis, and in such cases the 

 epithelium is replaced by a layer of tissue of loose tough texture contain- 

 ing nuclei, and attached to the serous membrane. Wide vessels crammed 

 with erythrocytes bore their way vertically to the surface through the 

 masses of fibrine. These vessels are often ramified and extremely thin 

 walled. The endothelia of these vessels have frequently sufiered slight 

 imbibition, their nuclei are vesicular and the chromatine attached to the 

 nuclear membrane. The walls are interspersed by frequent polymorphous 

 leucocytes, rare fusiform connective elements, and lymphocytes ; the 

 whole is held together by fibrillar interstitial tissue. 



Towards the lungs the fibrinous layer becomes arranged in parallel 

 layers, which have probably been exudated and coagulated in situ. 

 Around these layers leucocytes collect and organisation commences. The 

 damaged epitheha are, as is to be expected, rich in cells. The blood vessels 

 are dilated, often much ramified and even tangled. Here too an incrus- 

 tation of fibrine mixed with leucocytes, undergoing karyolysis and 

 karyorhexis is found around the vessels. 



As the process grows older more and more of the fibrine is dissolved 

 and replaced by organisatory tissues. The well-known retae of fibrine 

 merge slowly into the supporting tissue of the serosa. As consequence of 



