| | | Quaternary-- | | | Glacial | | | Champlain| | | Recent | | | CHAPTER III THE PHYSICAL LIMITATIONS OF EXISTENCE The tremendous strides made in the sciences of biology, histology, physiology, and psychology in the latter part of the last century, in connection with the development of the science of organic chemistry, have done much to unravel the life-mystery from a physical point of view. One by one the determining characteristics of the mentality of the _genus homo_ have dwindled down until to-day even reason in its broadest sense is granted by the most conservative to some of the vegetable forms of life, and any unbiased mind will have hard work to determine the difference between the so-called "Brownian" movement of particles of gamboge when macerated in a little water, or even of bits of camphor when dropped upon the surface of water, and the movements of the particles of a protoplasmic mass; although one is caused by temperature changes, and the other by chemism. The selectative growth of a vertex of a crystal in a saturated solution, and the claw of a crab, both of which have previously suffered the loss of their respective parts, are perhaps not so different as the words "organic" or "inorganic" would lead us to believe when applied as a classification to their principals. We know that in the life-process, as everywhere else, the law of substance and the law of the conservation of energy are held inviolate, and the theory which treats of life as a characteristic entity apart from the condition which makes it possible, is certainly false. The matter which composes the living body is chemically the same as that which we find everywhere. The fact that some living bodies have the power to form protoplasm out of its chemical elements or simple combinations of them, or only assimilate such protoplasm after it has been formed from inorganic matter, constitutes, in the broadest sense, the difference between the vegetable and the animal life, as we now know it. But, whether living or dead, the protoplasm has about the same composition, and, therefore, it must be that life _per se_ is in reality only the manifestation of a form of motion. Science, by deduction, teaches us to look upon the living body very much as a theoretically perfect motor-generator set, the line terminals of the dynamo being the feed wires of the motor. Such a machine, standing still, would be "dead" in all senses of the word, although, potentially, its integrity would be the same as when in operation. But, once put in motion, this machine would directly come up to speed, and maintain itself at its normal rate of rotation until something interfered with it, or set up resistance within its circuit.