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��r/fS SCIENTIFIC ytoyTiiLY

��separation of the ckromaiin. As prolopksm is now known to be the expression, so chro- matin is now known to be the seat of hered- , ity which Xageli (1884) was the first to discuss as having a physico-chemical basis; the " i(lio]i!asm " postulated in his theory boing realized in the actual structure of the cliromatin as developed in the researches of Hertwig, Strasburger, Kollikor, and Weis- niann, wJio independently and almost simul- taneously (1884, 1885) were led to the eon- elusion that the nucleus of the cell containa tile physical basis of inheritance and that the chromatin is its essential constituent." In the development from unicellular (Pro- tozoa) into multieellular (Uetazoa) oi^an- isnis the chromatin is distributed through the nuclei to all the cells of the body, but Boveri has demonstrated that all the body cells lose a portion of their chromatin and only the germ cells retain the entire ancestral heritage.

Chemically, the most characteristic pecu- liarity of chromatin, as contra3t«d with pro- toplasm, is its phosphorus content.'* It is also distinguished by a strong affinity for ceitain stains which cause its scattered or collected particles to appear intensely dark. Xuclein, which is probably identical with chromatin, is a complex albuminoid sub- stance rich in phosphorus. The chemical, or molecular and atomic, constitution of chro- matin infinitely exceeds in complexity that of any other form of matter or energy known. As intiniatotl above {pp. 7, 8) it not improb- ably contains undetected chemical elements. Experiments made by Oskar, Ounther, and I'jiula Hei-twig (1911-1914) resulted in the conclusion that in cells exposed to radium rays the seat of injury is chiefly, if not es- cliisivcly, in the chromatin:" these experi-

II Wilson, E. B., 1906, p. 403.

laMinchin, E. A., 1916, pp. 18, 19,

2> Kifhariis, A., 1915, p, 291.

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