148 



epithelial tissues. No inclusions similar to those found in variola and 

 pigeon pox were seen in the cells, despite the fact that all the proper 

 methods for staining them were used. 



All attempts to render the germs visible in sections were in vain, 

 although they are easily stained and demonstrated in smears treated with 

 gentian violet. Some of the specimens, it is true, showed fine dust-like 

 inclusions in the cells, but before I have elaborated a specific method of 

 staining, I do not care to regard this as being the stained lung-sickness 

 microbe. 



It is remarkable that the walls of the alveoles do not show any 

 inflammatory changes. In young stages, the alveolar capillaries are 

 filled with star-shaped fibrine deposits; in other parts, they are enlarged 

 and crammed with erythrocytes. The larger arteries and veins are mostly 

 choked with fibrine. Mixed or pure leucocyte-thrombus are frequent. 

 In advanced stages dam-like collections of leucocytes are observed, they 

 are peculiar to pleuro-pneumonia and will be described under the heading 

 interstitial connective tissue. 



The bronchioli and bronchi which have become affected show strong 

 epithelial desquamation and infiltration of the mucosa and subserous 

 connective tissue by leucocytes. Thick, mixed fibrinous fillings are 

 rare. Distinct dendritic injections formed only in two cases the cause of 

 the stepwise advance of the inflammation. The alveoles have 

 characteristics very different and changeable. The structure of the 

 interstities of the alveoles however, is absolutely constant in pleuro- 

 pneumonia. I came to recognise this peculiarity not from examination 

 of the lungs in the first place, but through comparison with the lesions 

 in the other organs. 



A rich comparative material of true croupous pneumonia and other 

 secondary pneumonias showed that the lesions in the structure of the 

 interstities of the alveoles were not the same as in pleuro-pneumonia. 

 The histological changes which principally take place around the blood 

 vessels are also found in the muscles, synovial membranes, and serous 

 membranes. 



In the beginning of the disease the endothehal tubiform lymphatic 

 vessels in the widened interstities of the lobuh ah^ the peribronchial septa 

 are greatly dilated. Frequently they are only filled with a finely granu- 

 lated albumen coagulum, frequently also strongly infiltrated with 

 fibrine. The walls of the vessels are absolutely free from pathological 

 changes. The typical specific changes soon supervene. The walls of the 

 distended lymphatic vessels become filled with leucocytes and conse- 

 quently indistinct. An exudate rich in fibrine spreads along the Ivmph 

 ducts through the whole interstitium, and condensing, encircles 

 capillaries, greater arteries and veins. The distance from the walls of 



