The system of mechanical and chemical functions which we have been occupied in reviewing, has been established only as a foundation for the endowment of those higher faculties which constitute the great objects of animal existence. It is in the study of these final purposes that the scheme of nature, in the formation of the animal world, opens and displays itself in all its grandeur. The whole of the phenomena we have hitherto considered concur in one essential object, the maintenance of a simply vital existence. Endowed with these properties alone, the organized system would possess all that is absolutely necessary for the continuance and support of mere vegetative life. The machinery provided for this purpose is perfect and complete in all its parts. To raise it to this perfection, not only has the Divine Architect employed all the properties and powers of matter, which science has yet revealed to man, but has also brought into play the higher and more mysterious energies of nature, and has made them to concur in the great work that was to be performed. On the organized fabric there has been conferred a vital force; with the powers of mechanism have been conjoined those of chemistry; and to these have been superadded the still more subtle and potent agencies of caloric and of electricity: every resource has been employed, every refinement studied, every combination exhausted that could ensure the stability, and prolong the duration of the system, amidst the multifarious causes which continually menace it with destruction.