210 THE HEASON WHY. 



"But they that wait upon the Lord shall renew their strength; they shall 



mount up with wings as eagles ; they shall run and not be weary ; 



and they shall walk and not faint." ISAIAH xx. 



which float in a watery fluid. The paste produced by mastication con- 

 sisted of a crude admixture of the atoms of food ; the cream (chyme) 

 formed from this in the stomach, presents to the microscope a 

 heterogeneous mass of matter, exhibiting no appearance whatever of 

 a new organic arrangement ; the milk (chyle) which is formed in 

 the intestines is found to contain a great - number of very small 

 molecules, which probably consist of some fatty matter ; as the 

 chyle progresses towards the thoracic duct (Fig. 50), it appjars to 

 contain more of these, and slight indications present themselves of 

 the approach towards a new organic condition. 



But wherever vitalisation begins, no human power can say 

 with confidence. Yet there can be no doubt that the blood is both 

 organised and vitalised, and that it consists of corpuscles, or little 

 cells, enclosing matters essential to life. 



893. Why does the blood circulate ? 



Because all the bones, muscles, blood-vessels, nerves, glands, 

 cartilages, &c., of which the body is composed, are constantly under- 

 going a change of substance. It is a condition of their life, health, 

 and strength, that they shall be " renewed," and the blood is the great 

 source of the materials by which the living temple is kept in repair. 



894. How is the body renewed by the blood ? 



Every drop of blood is made up of a large number of corpuscles, 

 each of which contains some of the elements essential to the wants 

 of the system. 



Let us, to simplify the subject, consider the blood vessels of the 

 body to be so many canals, on the banks of which a number of 

 inhabitants live, and require constant sustenance. The corpuscles 

 of the blood are the boats which are laclen with that sustenance, 

 and when the heart beats, it is a signal for them to start on their 

 journey. Away they go through the arch of the great acrta, and 

 some of the earliest branches which it sends off convey blood to 

 the arms. We will now for a moment dismiss the word artery, and 

 keep up the figure of a system of canals, with a number of towns 

 upon their banks. 



Well, away go a fleet of boats through the aorta canal, until 

 they reach a point which approaches Shoulder-town - t some of the 



