Page:The Scientific Monthly vol. 3.djvu/306

 300 THE SCIENTIFIC MONTHLY

the chromatin that the ideal form is not only preserved, but through subdivision carried into the germ cells of all the present and succeeding generations. The continuity of life since it first appeared in Archeo- zoic time is the continuity of the physico-chemical energies of the chro- matin; the development of the individual life is an unfolding of the energies taken within the body under the directing agency of the chromatin; and the evolution of life is essentially the evolution of the chromatin energies. It is in the inconceivable physico-chemical com- plexity of the chromatin that life presents its most violent contrast to any of the phenomena observed within the lifeless world.

Although each organism has its specific constant in the cubic con- tent of its chromatin, the bulk of this content bears little relation to the size of the individual. This is illustrated by a comparison of the chromatin content of the cell nucleus of Trillium, a plant about sixteen inches high, with that of Sequoia sempervirens, the giant redwood tree of California, which reaches a height of from 200 to 300 feet and attains an age of several thousand years (Fig. 5). The chromatin content of such a nucleus is measured bv the bulk of the chromosome rods of which it is composed. In the sea-urchin the size of the sperm nucleus, the most compact type of chromatin, has been estimated as about 1/100,000,000 of a cubic millimeter or 10 cubic microns in bulk."

Within such a chromatin bulk there is yet ample space for an incal- culable number of minute particles of matter. According to the figures given by Rutherford^' in the first Hale Lecture the diameter of the sphere of action of an atom is about 1/100,000,000 of a centimeter, or 1/10,000,000 of a millimeter, or 1/10,000 of a micron— the unit of microscopic measurement. The electrons released from atoms of mat- ter are only 1/1800 of the mass of the hydrogen atom, the lightest known to science, and thus the mass of an electron would be only 1/18,000,000 of a micron. These figures help us in some measure to conceive of the chromatin as a microcosm made up of an almost unlim- ited number of mutually acting, reacting and interacting particles ; but

24 E. B. Wilpon, letter of June 28, 1916.

25 It is necessary, obFerves Rutherford, to be cautious in speaking of the diameter of an atom, for it is not at all certain that the actual atomic structure is nearly so extensive as the region through which the atomic forces are ap- preciable. The hydrogen atom is the lightest known to science, and the average diameter of an atom is about 1/100,000,000 of a centimeter; but the negatively charged particles known as electrons are about 1/1800 of the mass of th© hydrogen atom. . . . These particles travel with enormous velocities of from 10,000 to 100,000 miles a second. ... The alpha particles produce from the neutral molecules a large number of negatively charged particles called ions. The ionization due to these alpha particles is measurable. ... In the phos- phorescence of an emanation of pure radium the atoms throw off the alpha particles with velocities of 10,000 miles a second, and each second five billion alpha particles are projected. Rutherford, Sir Ernest, 1915, pp. 113, 128.

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