144 ORGANS OF RESPIRATION. 



rior margin of its base. A deep fissure in a nearly similar 

 situation is observed on 'the right lung; but from it another fis- 

 sure branches out forwards, by which the right lung is divided 

 into three lobes. The internal face of the left lung is also ra- 

 ther more concave than that of the right, from the side of the 

 heart projecting into it. The right lung is more voluminous 

 than the left, which corresponds with the greater size of the 

 bronchus on this side, but its vertical diameter is not so great, 

 from the pressure of the liver from below; though this diameter 

 is increased by the descent of the liver when we are upright. 



Near the middle of the internal face of each lung are to be 

 seen the points of connexion with the bronchia, and with the 

 pulmonary vessels. Before these the anterior margin is thin, 

 and more or less winding where the lung is introduced between 

 the heart and the front parietes of the thorax. When the lungs 

 are fully inflated, only a very small portion of the front of the 

 pericardium can be seen between them. The posterior mar- 

 gin is thick, and rounded where it rests against the vertebral 

 column. 



The whole rounded circumference of the lung as well as its 

 base, though they are in contact with the parietes of the thorax, 

 do not adhere at any point to them. The connexion of the 

 lung, constituting its root, as it is called, and by which it is 

 maintained in its situation, is entirely on the side of its concave 

 face, where the pulmonary vessels and bronchia enter, and 

 though other attachments are frequently found springing from 

 different points of the thorax, they are purely the results of 

 disease. 



Of the Texture of the Lungs. 



Each lobe of the lungs is divided into a great many distinct 

 lobules, which adhere together by intermediate cellular tissue. 

 The marks of these divisions are apparent on the surface by 

 lines running in different directions, but they are made still 

 more distinct by tearing them asunder. The Lobules are sub- 

 divided into very fine air vesicles or cells, which may be con- 

 sidered as the terminations of the ultimate branches of the 

 bronchia. The opinion is generally held, that the cells do not 



