"1. By an examination of those notions which enter into all our reasonings and judgments on living things, it appears that we conceive animal life as a vortex or cycle of moving matter in which the form of the vortex determines the motions, and these motions again support the form of the vortex: the stationary parts circulate the fluids, and the fluids nourish the permanent parts. Each portion ministers to the others, each depends upon the other. The parts make up the whole, but the existence of the whole is essential to the preservation of the parts. But parts existing under such conditions are _organs_, and the whole is _organized_. This is the fundamental conception of organization. 'Organized beings,' says the physiologist,[79] 'are composed of a number of essential and mutually dependent parts.'--'An organized product of nature,' says the great metaphysician,[80] 'is that in which all the parts are mutually ends and means.' "2. It will be observed that we do not content ourselves with saying that in such a whole, all the parts are _mutually dependent_. This might be true even of a mechanical structure; it would be easy to imagine a framework in which each part should be necessary to the support of each of the others; for example, an arch of several stones. But in such a structure the parts have no properties which they derive from the whole. They are beams or stones when separate; they are no more when joined. But the same is not the case in an organized whole. The limb of an animal separated from the body, loses the properties of a limb and soon ceases to retain even its form. "3. Nor do we content ourselves with saying that the parts are _mutually causes and effects_. This is the case in machinery. In a clock, the pendulum by means of the escapement causes the descent of the weight, the weight by the same escapement keeps up the motion of the pendulum. But things of this kind may happen by accident. Stones slide from a rock down the side of a hill and cause it to be smooth; the smoothness of the slope causes stones still to slide. Yet no one would call such a slide an organized system. The system is organized, when the effects which take place among the parts are _essential to our conception of the whole_; when the whole would not _be_ a whole, nor the parts, parts, except these effects were produced; when the effects not only happen in fact, but are included in the idea of the object; when they are not only seen, but foreseen; not only expected, but intended: in short when, instead of being causes and effects, they are _ends_ and _means_, as they are termed in the above definition. "Thus we necessarily include, in our idea of Organization, the notion of an End, a Purpose, a Design; or, to use another phrase which has been peculiarly appropriated in this case, a _Final Cause_. This idea of a Final Cause is an essential condition in order to the pursuing our researches respecting organized bodies....