The mysterious ground, the efficient causes of vitality, and whether different lives differ absolutely or only in degree, He alone can know who not only said, “Let the earth bring forth the living creature, the beast of the earth after his kind, and it was so;” but who said, “Let us make man in our image, who himself breathed into his nostrils the breath of Life, and man became a living soul.” The third case which I would apply to my own attempt would be that of the inquirer, who, presuming to know nothing of the power that moves the whole machine, takes those parts of it which are presented to his view, seeks to reduce its various movements to as few and simple laws of motion as possible, and out of their separate and conjoint action proceeds to explain and appropriate the structure and relative positions of the works. In obedience to the canon,—“Principia non esse multiplicanda præter summam necessitatem cui suffragamur non ideo quia causalem in mundo unitatem vel ratione vel experientiâ perspiciamus, sed illam ipsam indagamus impulsu intellectûs, qui tantundem sibi in explicatione phænomenorum profecisse videtur quantum ab codem principio ad plurima rationata descendere ipsi concessum est.” 8 The arborescent forms on a frosty morning, to be seen on the window and pavement, must have _some_ relation to the more perfect forms developed in the vegetable world. 9 Thus we may say that whatever is organized from without, is a product of mechanism; whatever is mechanised from within, is a production of organization. 10 “The matter that surrounds us is divided into two great classes, living and dead; the latter is governed by physical laws, such as attraction, gravitation, chemical affinity; and it exhibits physical properties, such as cohesion, elasticity, divisibility, &c. Living matter also exhibits these properties, and is subject, in great measure, to physical laws. But living bodies are endowed moreover with a set of properties altogether different from these, and contrasting with them very remarkably.” (Vide Lawrence’s Lectures, p. 121.) 11 Much against my will I repeat this scholastic term, _multeity_, but I have sought in vain for an unequivocal word of a less repulsive character, that would convey the notion in a positive and not comparative sense in kind, as opposed to the _unum et simplex_, not in degree, as contracted with the _few_. We can conceive no reason that can be adduced in justification of the word _caloric_, as invented to distinguish the external cause of the sensation heat, which would not equally authorise the introduction of a technical term in this instance.