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upon the system of intermediate actions between the spring and the pointer. What thus struck his attention in the several parts of the watch he might probably designate by one general name of " relation:" and observing, with respect to all the cases whatever, in which the o igin and form tion of a thing could be ascertained by evidence, that these relations were found in things produced by art and design, and in no other things, he would rightly deem of them as characteristic of such productions. To apply the reasoning here described to the works of nature.
- The animal œconomy is full; is made up of these relations.
I. There are first, what, in one form or other, belong to all animals, the parts and powers.which successively act upon their food. Compare this action with the process of a manufactory. In man and quadrupeds, the allment is, first, broken and bruised by mechanical instruments of mastication, viz. sharp spikes or hard knobs, pressing against, or rubbing upon, one another: thus ground and comminuted, it is carried by a pipe into the stomach, where it waits to undergo a great chymkal action> .which we call digestion:
when when digested, it is delivered through an orifice, which opens and shuts as there is occasiony into the first intestine: there, after being mixed with certain proper ingredients, poured through a hole in the side of the vessel, it is further dissolved: in this state, the milk, chyle, or part which is wanted, and which is suited for animal nourishment, is strained off by the mouths of very small tubes, opening into the eavity of the intestines: thus freed from its grosser parts, the percolated fluid is carried by a long, winding, but traceable course, into the main stream of the old circulation; which conveys it, in its progress, to every part of the body. Now I fay again, compare this with the process of a manufactory; with the making of cyder, for example, the bruising of the apples in the mill, the squeezing of them when so bruised in the press, the sermentation in the vat, the bestowing of the liquor thus fermented in the hogsheads, the drawing off into bottles, the pouring out sot tile into'the glass. Let any one show me any difference Between these two cases, as to the point of contrivance. That which is at present: gnder our consideration, the " relation" noj/j "iib .... "t ; .: .... Qf
of the parts successively employed, Is not more clear in the last case, than in the first. The aptness of the jaws and teeth to prepare the food for the stomach, is, at least, as manifest, as that of the cyder-mill to crush the apples for the press. The concoction of the food in the stomach is as necessary for its future use, as the sermentation of the stum in the vat is to the persecution of the liquor. The disposal of the aliment asterwards; the action and change which it undergoes; the route which it is made to take, in order that, and until that, it arrive at its destination, is more complex indeed and intricate, but, in the midst of complication and intricacy, as evident and certain, as is the apparatus of cocks, pipes, tunnels, for transserring the cyder from one vessel to another; of barrels and bottles for preserving it till fit for use, or of cups and glasses for bringing it, when wanted, to the lip of the consumer. The character of the machinery is in both casts this, that one part answers to auo'her part, and every part to the final rc uk.
This parallel between the alimentary operation and some of the processes of art, might be 8 carried Carried further into detail. Spallanzani has remarked* a circumstantial resemblance between the stomachs of gallinaceous fowls and the structure of corn-mills. Whilst the two fides of the gizzard perform the office of the mill-stones, the craw or crop supplies the place of the hopper. When our fowls are abundantly supplied with meat they soon fill their craw; but it does not immediately pass thence into the gizzard. It always enters in very small quantities, in proportion to the progresses trituration: in like manner as in x mill a receiver is fixed above the two large stones which serve for grinding the corn; which receiver, although the corn be put into it by bushels, allows the grain jto dribble only in small quantities into the central hole in the upper mill-stone.
But we have not done with the alimentary history. There subsists a general relation between the external organs of an animal by which it procures its food, and the internal powers by which it digests it. Birds of prey, by their talons and beaks, are qualified to seize and devour many species, both of other
* Diss. 1. sec. Kr.
birds, and of quadrupeds. The constitatioa of the stomach agrees exactly with the form of the members. The gastric juice of a bird of prey, of an owl, a falcon, or a kite, acts upon the animal fibre alorte ; ,will not act upon seeds or grasses at all. On the other hand, the conformation of the mouth of the sheep or the ox is suited for browsing upon herbage. Nothing about these animals is fitted for the pursuit of living prey. Accordingly it has been found by experiments, tried not many years ago with perforated balls, that the gastric juice of ruminating animals, such as the sheep and the ox, speedily dissolves vegetables, but makes no impression upon animal bodies. This acccrdancy is still more particular. The gastric juice even of graminivorous birds, will not act upon the grain, whilst whole and entire. In performing the experiment of digestion with the gastric juice in vessels, the grain must be crushed and bruised, before it be submitted to the menstruum, that; is to fay, must undergo by art, without the body, the preparatory action which the gizzard exerts upon it within the body, or no digestion will take place. So strict is the relation between the offices assigned to the digestive or'. . 6 gan;