"Certainly, there may be a comparison; for a superficial and rapid survey of the animal body may convey the notion of an apparatus of levers, pulleys, and ropes--which maybe compared with the spring, barrel, and fusee, the wheels and pinions, of a watch. But if we study the texture of animal bodies more curiously, and especially if we compare animals with each other--for example, the simple structure of the lower creatures with the complicated structure of those higher in the scale of existence--we shall see, that in the lowest links of the chain animals are so simple, that we should almost call them homogeneous; and yet in these we find life, sensibility, and motion. It is in the animals higher in the scale that we discover parts having distinct endowments, and exhibiting complex mechanical relations. The mechanical contrivances which are so obvious in man, for instance, are the provisions for the agency and dominion of an intellectual power over the materials around him. "We mark this early, because there are authors who, looking upon this complexity of mechanism, confound it with the presence of life itself, and think it a necessary adjunct--nay, even that life proceeds from it: whereas the mechanism which we have to examine in the animal body is formed with reference to the necessity of acting upon or receiving impressions from, things external to the body--a necessary condition of our state of existence in a material world. "Many have expressed their opinion very boldly on the necessary relation between organization and life, who have never extended their views to the system of nature. To place man, an intelligent and active being, in this world of matter, he must have properties bearing relation to that matter. The existence of matter implies an agency of certain forces;--the particles of bodies must suffer attraction and repulsion; and the bodies formed by the balance of these influences upon their atoms or particles must have weight or gravity, and possess mechanical properties. So must the living body, independently of its peculiar endowments, have similar composition and qualities, and have certain relations to the solids, fluids, gases, heat, light, electricity, or galvanism, which are around it. "Without these, the intellectual principle could receive no impulse--could have no agency and no relation to the material world. The whole body must gravitate or have weight; without which it could neither stand securely, nor exert its powers on the bodies around it. But for this, muscular power itself, and all the appliances which are related to that power, would be useless. When, therefore, it is affirmed that organization or construction is necessary to life, we may at least pause in giving assent, under the certainty that we see another and a different reason for the construction of the body. Thus we perceive, that as the body must have weight to have power, so must it have mechanical contrivance, or arrangement of its parts.