92 



PHYSIOLOGY AND TEMPERANCE. 



concave, and has a fissure, in which are the air-tubes and 

 vessels entering the lungs. 



Each lung is divided into two lobes by a long, d^ep fissure. 

 The upper lobe of the right lung is partially divided by a 

 short fissure, so that it is said to have three lobes. The right 

 lung is somewhat the larger, on account of the heart being 

 placed a little to the left side. 



WINDPI PB ^ n substance the lung is 



of a light porous or spongy 

 nature, and very elastic. 

 This lightness of texture 

 is largely due to the pres- 

 ence of air, which is never 

 entirely expelled, even 

 when we force out all we 

 can. Examined minutely, 

 we find the lung to consist 

 of lobules, closely connected 

 together, but yet quite dis- 

 tinct from one another. 

 Each lobule is formed of 

 one of the divisions of a 

 bronchial tube, with its 

 air-cells, and of the divisions of the pulmonary vessels. In 

 each are also found nutritious vessels and nerves. There are 

 a large number of air-cells to one branch of a small bronchial 

 tube. They cluster around it like a bunch of grapes on a 

 stem. If the stem were hollow, and each grape an empty sac 

 communicating with it, to blow into the stem would give a 

 fair example of how the air fills up the air-cells every time we 

 take in a breath. Think how small these air-cells must be, 

 when seventeen hundred of them cluster around one small 

 tube. Yet each cell is separated from the other by a fine, 

 thin partition. In this delicate, thin wall is a dense network 



FIG. 29. The Lungs and Heart, 

 viewed in front. 



