HOW TO KNOW HIM. 23 



I am not writing a minute anatomical description of 

 the chest ; and I need only say that it is bounded on the 

 front by the neck, on either side by the shoulder-blades 

 and the ribs, underneath by the breast-bone, above by 

 the spine, and in the rear by the diaphragm, which acts 

 as a division between it and the intestines. Draw a line 

 from the hindermost point of your saddle until it touches 

 the back-side of the girths, near the breast-bone, and 

 you see with sufficient accuracy the position of the dia- 

 phragm. It is a large sheet of muscular tissue, reaching 

 from side to side in such a way as to completely divide 

 the power separating it into two great cavities. It is 

 pliable in texture, and, when moved backward or for- 

 ward, lessens or enlarges either of the cavities between 

 which it is drawn. The front one of these two cavities 

 is occupied almost entirely by the heart and lungs. 

 Here they dwell almost alone in the home which Nature 

 has provided for them, and which they monopolize. The 

 heart is small in size, and alters little, whether in repose 

 or action, sickness or health. Not so with the lungs : 

 they expand and shrink with every breath. In their 

 substance they are highly elastic, and capable of being 

 enormously distended ; and each distention is followed 

 with a commensurate collapse. To accommodate this 

 mighty expansion, which results from every aspiration 

 made by a horse when in violent action, Nature has 

 made a wonderful provision. When the aspiration begins, 

 the arch made by the ribs is elevated, and the diaphragm 

 is drawn back, in order that the cavity between them 



