This is a very wonderful fact, but no less true than wonderful, that dead matter which, but a little while ago, was being ground by the teeth, softened by the saliva, and solved by the gastric juice and bile, has now acquired _life_. Nobody can tell the precise stage or moment when it began to live. But somewhere between the stomach and the lungs, melted by the gastric juice, softened by the secretion of the pancreas, separated by the bile of the liver, macerated by the muscular fibres of the bowels, taken up by the absorbents, warmed by the heat of the body, and ærated in the lungs, it has by one, or by all of these processes combined, been changed from the dead to the living state, and now forms part of the _vital fluid of the system_. CHAPTER XLIII. 892. _Why do we know that the blood has become endowed with vital powers?_ Because, in the course of its formation, it has not only undergone change of condition and colour; but, if examined now by the microscope, it will be found to consist of millions of minute cells, or discs, which float in a watery fluid. The paste produced by mastication consisted 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 appears 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. [Verse: "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 XL.] 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 undergoing 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.