else tliaii lympli vessels or ducts, liave generally become thicker and 

 more callous. The rounded cavities are turgid with exudate, often even 

 filled with small, firm, friable, dark yellow thrombus. One can cut them 

 open and squeeze out the contents. 



The septa look like rosaries in consequence of the transparent hollows. 

 As the processes becomes older the appearance also gets more uniform; 

 the neoplastic connective tissue takes up most of the space, and the septa 

 becomes broader, opaquer, and more callous. Septa 3 cm. thick are not 

 rare. The piihnonary tissue is divided up into more or less square areas 

 by the interstities, so as to give a fanciful resemblance to a chess board. 



The septa close up to the greyish-white, much-thickened subserosa 

 if the pleura is affected, and if its morbid changes take place pari passu 

 with those in the lungs. On removing the yellowish-white attached 

 exudate, one recognises bread opaque bands of connective tissues corre- 

 sponding to the outUnes of the lobuli. 



A remark on the modus of infection may here be interesting. In a 

 specimen of a lung of an ox (belonging to the herd of this laboratory) a cir- 

 cumscript serous fibrinous infiltration of the peribronchial lymphatic 

 vessels was found. 



The processes seemed to have the tendency to spread from the major 

 bronchus to the interalveolar tissue. I feel inchned to beheve that most 

 pleuro-pneumonia infections originate in the bronchial and peribronchial 

 lymph vessels and spread pe? continuitatem to the rest of the lung. Be 

 that as it may, it is certain that in the initial stages we have before us 

 pathologic-anatomically SaU interstitial pneumonia due to serous fibrinous 

 lymphangitis. The inflammation, although originally a purely interstitial 

 disease, an uncomplicated puhnonal lymphangitis, sooil spreads to the 

 neighbouring alveoli, giving the appearance in chronic cases of a croupous 

 pneumonia. Unmixed pleurogene pneumonia seem to be rare, that is 

 to say pneumonias in which the process has spread secondarily from the 

 pleura, although it has been postulated that only in such cases does one 

 find the well-known characteristic macroscopic lesions. It is certain that 

 the interstitial pneumonia of lung-sickness is not a recuperative reparatory 

 process, such as pneumonias caused by foreign bodies or traumatic 

 pneumonias or abscesses are, for the changes in the septa take place at a 

 period when there can be no question of reconvalescence. 



Deposits of fibrine in the vessels of the interstities are caused by the 

 influence of the exudation, which spreads from the lymph vessels to the 

 perivascular tissue ; the blood vessels being very often thrombosed. 

 The same fate awaits the pulmonary blood vessels, which, compressed by 

 infiltrated lung tissues, can pass through all stages of thrombosis and 

 resolutioii. Dark red thrombus, attached to the intima are most frequently 

 surrounded by the adventitia and perivascular connective tissue as a 

 tough yellowish-grey ring. Fihform or lobular appendages of the intima 



