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Show 8 THE PltESENT CONDITION common Horse. Suppose we wish to understand all about the Horse. Our first object must be to study the structure of the animal. The whole of his body is inclosed within a hide, a skin covered with hair; and if that hide or skin be taken off, we find a great mass of flesh, or what is technically called muscle, being the substance which by its power of contraction enables the animal to move. These muscles move the hard parts one upon the other, and so give that strength and power of motion which renders the Horse so useful to us in the performance of those services in which we employ him. And then, on separating and removing the whole of this skin and flesh, you have a great series of bones, hard structures, bound together with ligaments, and forming the skeleton which is represented here. In that skeleton there are a number of parts to be Tecognizecl. This long series of bones, beginning from the skull and ending in the tail, is called the spine, and these in front are the ribs; and then there are two pairs limbs, one before and one behind; and these are what we all know as the fore-legs and the hind-legs. If we pursue our researches into the interior of this animal, we find within the framework of the skeleton a great cavity, or rather, I should say, two great cavities,-one cavity beginning in the skull and running through the neck-bones, along the spine, and ending in the tail, containing the brain and the spinal marrow, which are extretnely important organs. The second great cavity, commencing with the mouth, contains the gullet, the stomach, the long intestine, and all the rest of those internal apparatus which are essential for digestion; OF ORGANIC NATURE. 9 and then in the same great cavity, there are lodged the heart and all the great vessels going from it; and, besides that, the organs of respiration-the lungs; and then the kidneys, and the organs of reproduction, and so on. Let us now endeavour to reduce this notion of a horse that we now have, to some such kind of simple expression as can be at once, and ·without difficulty, retained in the mind, apart from all minor details. If I make a transverse section, that is, if I were to saw a dead horse across, I should find that, if I left out the details, and supposing I took my section through the anterior region, and through the fore-limbs, I should have here this kind of section of the body (Fig. 1). Here would be the upper part of the animal-that great mass of bones that we spoke of as the spine (a, Fig. 1.) I-I ere I should have the alimentary canal (b, Fig. 1). flere I should have the heart (c, Fig. 1); and then you see, there e would be a kind of e FIG.l. double tube, the whole being inclosed within the hide ; the spinal marrow would be placed in the upper tube (a, Fig. 1 ), and in the lower tube (b, Fig. 1) there would be the alimentary canal and th~ heart; and here I shall have the legs proceeding from each side. For simplicity's sake, I represent thmn merely as stumps (e e, Fig. 1). Now that is a horseas mathematicians would say-reduced to its 1nost sim- |