6. Ibid., p. 86.

7. Ibid., p. 89.

8. Ibid., p. 170.

9. W. BRAGG, Concerning the Nature of Things, pp. 14, 15.

10. B. MOORE, Origin and Nature of Life.

11. С. С. Аввотт, op. cit., p. 46.

12. J. BARRELL in Lull, op. cit., p. 39.

13. C. SCHUCHERT in Lull, op. cit., p. 48.

14. M. WHITNEY, Soil and Civilization, pp. 43-44.

15. С. С. Аввотт, ор. cit., pp. 51, 52.

16. C. SCHUCHERT in LULL, op. cit., pp. 47, 48.

17. Ibid., p. 67.

18. Ibid., p, 69.

CHAPTER II

LIFE, ITS NATURE AND DISTRIBUTION

The search for truth is in one way hard and in another easy. For it is evident that no one can master it fully nor miss it wholly. But each adds a little to our knowledge of nature, and from all the facts assembled there arises a certain grandeur. -ARISTOTLE.

The atoms of most of the elements do not lead an isolated existence but combine to form molecules. In a few substances such as mercury this does not happen, and atom and molecule are synonymous terms. We say that they are drawn together by the power of chemical affinity but, as is so often the case, that is a term rather than an explanation. The atoms of different elements may join to form molecules of a new substance. Most of these inorganic compounds are simple. When, however, we come to the organic molecules we find hundreds or even thousands of atoms uniting. This increased complexity attracts our attention. At once the question rises in our minds as to when, where, and how, such a combination into living forms took place. To this question no positive answer can be given. In the past men felt compelled to posit the existence of some "vital principle" which, in some way, entered into matter and gave it life. Again we have a term and not an explanation. In reality we do not understand matter. We cannot visualize its creation any more than its destruction. What we can do, if we are fortunate, is to observe what matter does and under what conditions. The same holds true of life.

ORGANIC COMPOUNDS

At the outset let us notice that the difference between inorganic and organic things does not lie in the elements of which they are made, although only a few of them are known to be used in organisms. Those which have been found are hydrogen, oxygen, nitrogen, fluorine, iodine, chlorine, iron, magnesium, sodium, potassium, manganese, lithium (?), phosphorus, sulphur, and carbon. All of these are ordinarily substances and the market value of the materials of which a man's body is made is perhaps ninetyeight cents.

The terms which we have used-organic and inorganicgive the clew to the answer. Living beings have a different organization and behave in a different way. There is no evidence that any new material has been used. In view of this fact we have to assume that at some time in the history of the world the conditions were such that matter assumed organic form and life began, just as we have seen that water vapor formed when conditions were favorable. What these conditions were that favored life we do not know. There is no evidence that matter has assumed organic form at any time within the knowledge of man in spite of his hoary faith in spontaneous generation. This is, however, a confession of ignorance, not a statement of fact. No organism known to man can live and reproduce at the temperature of boiling water (212°) nor below the freezing point (32°). Life then could not have existed until the surface of the earth had cooled below the boiling point. All that we know is that when conditions were favorable life appeared. Moore would have us believe that this was due to a "law of complexity" and since he accepted the nebular hypothesis, he would have located the Garden of Eden near the poles of the earth, probably, as the place where the necessary temperature would have first existed. If, however, the planetary hypothesis is accepted, the climate may have been substantially the same over all the earth for long periods. We have, then, no idea where or when life appeared although we may establish certain limits. If we look about us to-day we observe that wherever life is possible, there life is, and we may be justified in holding that the same must have been true at all time. We may be justified also in holding that life first appeared in the water or in moist earth, for the simplest types we know exist under such conditions.

Primitive Protoplasm

Even if we assume that matter takes an organic form under certain conditions, we have no idea of the characteristics of this original protoplasm. The colloids have large molecules but the colloid is far from being an organism. On the other hand the lowest organisms we know are far too complicated to have been the first living products of nature. Probably we shall have to say with Moore that "the territory of this spontaneous generation of life lies not at the level of bacteria, or animalculæ, springing forth into life in dead organic matter, but at a level of life lying deeper than anything the microscope can reveal, and possessing a lower unit than the living cell, as we form our concept of it from the tissues of higher animals and plants." 1 Moore touches here on a point that should not be forgotten. Just as there are bits of matter too small to be seen so there are living organisms beyond our vision to-day which some day man may be able to study.

The initial organisms were probably like bacteria, the first organic form capable of the capture of energy and its storage. As Osborn says, bacteria appear to lie halfway between our hypothetical chemical precellular stages and the chemistry and definite cell structure of the lowliest plants or algæ. These creatures are often known more by the chemical and other reactions which they bring about than by their form.... All of them, however, from the smallest to the largest, while among the simplest of organisms, are nevertheless highly complex. Next in the scale of life come the algæ, distinguished by the possession not alone of protoplasm, but of leaf green, or chlorophyl, as well. Which is the older substance it is difficult to decide. Certain authorities claim that it is chlorophyl, without which protoplasm cannot be manufactured in the living organism. For the chlorophyl in the presence of light has the power of utilizing carbon dioxide and water and manufacturing starch. Protein formation comes next and needs as raw materials not only the already made starches, but certain nitrogenous compounds, which are derivable from animal waste or decay, but can also be made by certain nitrogen-fixing bacteria. The animal can make neither starches nor proteins, but must take them ready made from the plant.2

There is one compound or group of compounds which is absolutely diagnostic of life stuff in that the substances are never found under any circumstances other than in the bodies of organisms, living or dead. These are the proteins, composed of carbon, hydrogen, oxygen, and nitrogen, with traces of other elements, such as sulphur. The molecules of protein are so complex that their atoms, instead of being numbered by the twos or threes, as in so many chemical substances, are actually in the thousands. Protein is an absolutely essential constituent of protoplasm, which in its turn is the primary building material of all organisms of whatever sort, whether plant or animal. Other organic compounds, in addition to the proteins, are the fats and oils, and the starches and sugars. None of these substances occurs in nature except as an organic product. There are, in addition, several other materials, such as water, common salt, and the various skeleton- or shell-forming substances, containing lime or silica.

...

Physically, protoplasm is a viscous, semi-fluid mass of matter, often appearing granular beneath the microscope, again emulsoid in structure. Its color is grayish pellucid, the color of clear glass or of water.4

Physiologically, it possesses properties which are distinctively vital, as compared with the inertness of the inorganic, such as sensitivity, conductivity, and irritability, whereby stimuli are received, transmitted, and responded to throughout the cell, for