406 



Bardeen for help and many valuable suggestions, during the time I 

 was working on this subject. 



Among those who have made a study of the cartilage, goblet cells, 

 ciliated epithelium and glands of the bronchi, Kölliker, Franken- 

 hauser and Schulze are the only ones who seem to have paid any 

 special attention to their points of disappearance. In giving a brief 

 account of the results obtained by them, and a number of other in- 

 vestigators, the subject will be taken up in the following order : carti- 

 lage, goblet cells, cilia and glands. 



Cartilage, With respect to cartilage, the main difference be- 

 tween Kölliker and Frankenhauser is that Kölliker found it to 

 disappear in bronchi 0,85 mm in diameter, while Frankenhauser found 

 it to disappear in bronchi 0,4 mm in diameter. Both of these obser- 

 vations were made on the lung of man. Schulze who worked on 

 various vertebrates says cartilage disappear in bronchi 1 mm in dia- 

 meter. Other authorities who find the point of disappearance to be 

 1 mm are Spalteholz, Henle, Krause, Schafer and Stöhr, The 

 last named make this statement in textbooks of histolology and anatomy, 

 therefore it must be restricted to man alone. 



Goblet cells. With respect to goblet cells Kölliker says they 

 are lacking in the respiratory bronchi of man. The smallest bronchi 

 observed to have goblet cells measured 0,42 mm in diameter. 



All that Frankenhauser says is that they are present in middle- 

 sized bronchi of man. Schulze states that the goblet cells are lost 

 at the point of transition of the bronchi into the alveolar passages. 



Ciliated cells, Kölliker says they are still present in the 

 respiratory bronchi of man which means bronchi under 0,5 mm dia- 

 meter. He makes the statement that ciliated cells extend further 

 than goblet cells. As goblet cells extend to bronchi 0,42 mm in dia- 

 meter, therefore ciliated cells must extend a little further, Franken- 

 hauser makes the statement that ciliated, epithelium is still present 

 in bronchi 0,3 mm diameter. This was observed in the lung of the cat. 



Schulze says the cilia are lost at the point of transition of the 

 bronchi into the alveolar passages. 



Glands, Kölliker found them to disappear in bronchi of man 

 1 mm in diameter, 



Frankenhauser says with reference to man, that glands are very 

 rare in bronchi under 0,4 mm diameter. In the cat he says, he has 

 found a few in bronchi 0,3 mm in diameter. Schulze says they dis- 

 appear in bronchi of about 1 mm diameter. This last statement is 

 not restricted to any certain animal, Remak says they are found in 



