LIFE AND CRYSTALIZATION. 159 the measures of the angles, differing in different bodies. Different bodies assume different forms as represented in fig. 14. FIG. 14. The same body crystalizes sometimes in more than one form, as Carbon, which becomes a regular octahedron, or cube, or some figure geometrically connected with these in the diamond, but a short six-sided prism in graphite, which has no geometrical relation to the former. Sulphur crystalizes in two forms. In plants is found a large number of crystalized bodies, called Raphides, from the resemblance which some of them have to a needle-papis. They were originally discovered by Malpighi. These minute crystals are deposited from the vegetable secretions. They assume a variety of forms, and differ in their chemical composition; the needleshaped Raphides being composed of phosphate of lime, and the stellate of the same oxide in combination with oxalic acid. Some are made of tartarate, citrate, and malate of lime, and are repre 160 LIFE AND CRYSTALIZATION. sented in figures 15 and 16, and vary in size from NHA one-fortieth to one-thousandth part of an inch in diameter. Plants are often rendered brittle by them, as the Cacti, &c. It is well known that bones, teeth, and shells are formed by the deposition of calcareous matter in the animal cells. If a piece of bone, dentine, or shell be examined by the aid of a good microscope it will be found to be composed of an unlimited number of inorganic (ossific) granules, globular or ellipsoidal in form, each surrounded by a soft covering of animal matter. The earthy or animal matter may be removed by macerating; for the removal of the former in dilute Hydrochloric Acid, and of the latter in a solution of Caustic Potash. Some regard these crystaline bodies in vegetables and animals as the earliest manifestation of life (Grinrod), or as the transition state of matter from the inorganic to the organic form (Geoffrey St. LIFE AND CRYSTALIZATION. 161 Hilaire); and since it is an easy matter to formwithout any supernatural aid-crystals generally, and even to produce Raphides, by injecting limewater into the vegetable cells, and macerating the whole substance in a solution of oxalic or phosphoric acid; and form artificial ossific granules, such as those found in bone, dentine, and shell, by a proper arrangement, in a wide-mouthed bottle, of carbonates of lime and potash or soda in solution, together with gum or albumen, it is, by some imagined that it will be possible for man-by his skill alone to transform inorganic matter into vegetable and animal substances of the highest form. The limits of these Notes will not allow a thorough examination or refutation of this theory. It may be stated, however, that the chemical nature of crystals harmonizes with that of inorganic rather than of organic matter; and that a crystal ever remains a crystal, unless it is reduced to its amorphous state; and that a crystal has never once been found to change into the form ever assumed by organized beings to which reference has been made in the text. The shapeless mass may be seen changing into crystals, and until one of these crystals has been seen making a nearer approach to the form which characterizes organic matter, than the crystal itself, the theory must be regarded as perfectly chimerical. M 162 CENTRAL ORGAN OF PROPULSION. NOTE G.-CENTRAL ORGAN OF PROPULSION. "Being propelled by a central force to every part of the body, &c."-Page 11. The analogy existing between the majority of living beings in the possession of what is called in the higher animals a heart, or generally a central organ of propulsion, is a most interesting and instructive enquiry; the fact illustrating the limited unity and the universal diversity of things. The accompanying diagram, fig. 17, is an ideal representation of the heart and circulating appa ratus in Mammals and Birds, which form the highest division of Vertebrates. The oxygenized or arterial blood is represented by the red, and the venous or unoxygenated blood by the blue colour. The blood having passed through the system, supplying its wants and removing its wastes, returns through the veins, and is poured into the Right CENTRAL ORGAN OF PROPULSION. 163 Auricle of the heart by the Vena Cava. By the contraction of the right auricle the blood is forced into the Right Ventricle, which again contracts, driving the blood through the Pulmonary Artery into the lungs, where it is exposed to the action of the oxygen taken in by the act of Respiration. Here it parts with the greater part of the carbonic acid it held in solution, and passes, surcharged with oxygen, through the Pulmonary Veins to the Left Auricle of the heart, by the contraction of which it is driven to the Left Ventricle, which propels the life sustaining current through the Aorta to the smaller arteries, and thence to every part of the body. By an examination of the above diagram it will be seen that all the blood of Mammals and Birds is brought into contact with the air during each circulation, which accounts for their warmth, active and energetic habits, and frequent requirement of food. The next class is the Reptilia or Reptiles. These animals have cold blood, inactive habits, and possess great power of endurance. Only a part of the blood becomes oxygenized during one circulation, the heart being divided into three lobes or compartments, instead of four, as seen in fig. 18. There being but one ventricle, the pure and impure |