12 RESPIRATION, CIRCULATION, DIGESTION DIAGRAM 1. 



it is this which is felt to beat, it was said that the heart was on 

 the left. The two lungs fill the greater part of the chest to the 

 right and left, but without adhering to its surface, against which 

 they slide. 



The Abdomen. The cavity of the belly, or of the abdomen, ex- 

 tends from the diaphragm to the pelvis. It is protected above 

 only by the last ribs, and below by the hip bone. The liver is 

 situated on the right, in the upper part of the abdomen. This 

 secretes the bile, called also the yall, which collects in a small 

 bladder called the gall-bladder. Further to the left is the 

 stomach, a kind of closed bag furnished with only two openings 

 that of the oesophagus, by which food enters, and that of the 

 intestines, by which it passes out. To the left of the stomach, 

 in the upper part of the abdomen, is the spleen. It is there 

 where we feel pain when we have a stitch in the side from having 

 run too much. It was thought on this account that animals 

 would be able to run faster if their spleen was removed, but 

 this operation is no longer practised. Below the liver, the 

 stomach, and the spleen, the intestines are coiled, which are at 

 least four or five times the length of the body. They form a 

 long tube, narrow throughout the first part of its course, which 

 is called the small intestines, and larger towards the end, where 

 it is called the large intestines. Behind the intestines are the 

 kidneys. They secrete the urine, which drops into the bladder 

 before being expelled from the body. 



RESPIRATION. It is not sufficient for man to eat to sustain 

 life ; he must also breathe atmospheric air. This is composed 

 of a mixture of three gases, which it is necessary to mention. 

 The first is called oxygen, the second azote or nitrogen, aud 

 the third carbonic acid. These three gases are mingled in very 

 unequal proportions, and we cannot separate them at will ; but 

 chemistry teaches us the properties of each of them. 



Oxygen is indispensably necessary to the life of animals, as 

 well as for the combustion of wood or coal. Where there is no 

 oxygen, all ilarae is extinguished, and every animal dies. For 



