262 



MANUAL OF HISTOLOGY. 



alcohol, the lines between the epithelial plates can be demon- 

 strated. The nuclei can be stained with carmine. 



Some of the cells are converted into hyaline plates. The 

 alveolar epithelium of the human lung is not so readily demon- 

 strated as that of animals, principally because too long a time 

 usually elapses between death and the post-mortem dissection. 

 In some traumatic cases an autopsy can be made early, and as 



FIG. 112. Interior of an alveolus. Lung injected with a solution of nitrate of silver to show the lines 

 between the alveolar epithelial cells. F. E. Schulze. 



favorable opportunity had of examining these structures. They 

 can be shown very well in fresh sections cut with Valentin's 

 knife. 



The spaces between the alveoli and acini contain the elastic 

 fibres mentioned above, together with a few oval connective- 

 tissue nuclei and muscular elements. The lobules are held 

 together by thin septa of connective tissue. The connective 

 tissue is also found in the angles of division of the lobular 

 bronchi and bronchioles. 



The muscle-cells may be identified by their elongated, 

 fusiform nuclei. A further proof of their existence is found 

 in certain cases of cirrhosis of the lung, in which many distinct 

 muscular fibres are found in the new connective tissue. 1 



The branches of the pulmonary artery follow the course 



1 Buhl : Lungenentz. Tuberculosis, u. Schwindsucht, Munchen. 1873, S. 358. 



