4Ü8 



taneously with the cilia in the lung of man and of the cat. The 

 finest bronchus observed to have goblet cells measured 0,48 mm in dia- 

 meter. Several were found in bronchi between 0,5—0,6 mm in diameter. 



Ciliated epithelium. The exact point of disappearance of 

 the cilia was rather difficult to determine. 



In larger bronchi, where they were numerous, they were found to 

 be especially numerous around the mouths of glands. They were seen 

 to extend in aways along the duct until it branched, and then they 

 disappeared. As the finer bronchi were approached, it could be noti- 

 ced that the cilia became scarcer in parts distant from the ducts, 

 while they persisted around these, and in the ducts themselves. They 

 grew gradually scarcer even in these positions and finally disappeared 

 in bronchi between 0,5 — 0,6 mm in diameter. The columnar epithelium 

 began to disappear just before this, and although not entirely absent 

 at the point where the cilia began to disappear, it is well interspersed 

 with cuboidal epithelium. From this it will be seen that there appears 

 to be a relationship between cilia and columnar epithelium. The cilia 

 occur only on columnar epithelium though not all columnar epithelium 

 are ciliated. But where the ciliated disappears, there the columnar 

 epithelium becomes scarcer, and it disappears a short distance beyond 

 this point, becoming low columnar, then cuboidal epithelium. 



Glands. These were found to extend into the finest bronchi, 

 disappearing just before the bronchi break up into the terminal bronchi. 

 They were especially abundant at the angles formed by the union of 

 bronchi. Here they were massed together in great numbers even in 

 bronchi where glands were few in number in other parts of the wall. 

 The ducts of these glands narrow just before emptying into the bron- 

 chus, and in the bronchi where cilia are found are lined with these. 

 After the duct passes through the muscular layer, following it towards 

 the glands, it divides. Not more than two branches have been ob- 

 served at this point. These in turn may divide into other branches, 

 which finally end in the glands themselves. Satisfactory proof of the 

 presence of cilia in the glands has not been found, and they are not 

 believed to be there. The main duct does not necessarily branch after 

 penetrating the muscle layer. It has been observed especially in the 

 finer bronchi to swell out immediately into the gland. In the larger 

 bronchi where the epithelium is columnar, the cells in the beginning 

 of the duct may be columnar or of a low columnar type, but they 

 become distinctly cuboidal in type further along in the duct. In the 

 glands the cells are of a cuboidal or low cuboidal type. The cells 

 are arranged around a small central lumen, and are somewhat wedge- 



