CHAPTER X. 



Sketch of the Internal Organisation of the Horse. 



THE LUNGS. 



PLATE IX, Fig. i, etc. 



The lungs are two spongy bodies formed for the 

 purpose of breathing. They are contained in the 

 lateral regions on each side of the chest, a^ a, a, 

 separated from each other by the mediastinum and 

 heart, which occupy the middle region. The lungs 

 are two in number, — the right and the left, partitioned 

 from each other by the mediastinum. They are 

 further divided into lobes, — that on the right side, 

 which is the larger of the two, consists of three lobes 

 and the left has only two. These lobes are merely- 

 partial divisions, of variable extent, which serves to 

 adapt them more accurately to the cavities of the 

 chest, and at the same time render them fitter for 

 the purposes of expansion and contraction. When the 

 windpipe enters the chest, it is divided into two 

 branches, one extending to each lung ; and when 

 these enter the substance of the lungs, they separate 

 into numerous branches, each terminating in a little 

 bag or cell. These bear a considerable resemblance 

 to minute bunches of grapes. Around these cells are 

 spread innumerable blood-vessels, being the extreme 

 ramifications of those which conveyed the blood from 

 the right side of the heart to the lungs, and the com- 



