Page:Popular Science Monthly Volume 30.djvu/446

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THE POPULAR SCIENCE MONTHLY.

limbs trembling as if in a paroxysm of epilepsy. Two persona came forward, and, taking her by her arms, raised her to her feet. . . . The little performance was enacted to please the white man."

 

The Life-Term of Animals and Plants.—Dr. August Weissman regards the life-terms of animals and plants not as fixed and the results of internal processes, but as modifiable according to external conditions and the incidents of the struggle for existence. The idea that the immediate cause of death is the wearing away of the tissues does not agree with the theory that the tissues are undergoing constant changes of substance, resulting in alteration and restoration, nor with the fact that some kinds of cells go on reproducing themselves indefinitely, or with the other fact that some animals perish, when apparently in full vigor, immediately after performing the generative function. It would seemingly be better to look for the cause of death in the terminability of the reproductive powers; and we might explain the difference in the possible life-terms of different species by supposing that the number of cell-generations which can proceed from the egg-cells normally differs in each species. A perishable material is provided for the inevitable wear and destruction of the body, and the function of unlimited increase has been confined to a smaller number of cells, which we call reproductive cells. We have in this and in some other facts justification for supposing that the life-force is essentially and originally unlimited. This appears to be actually the case with some of the lower organisms. They may be killed in various ways, it is true; but, so long as the conditions essential to life are around them, they live, and bear within themselves the conditions of never-ending existence. The process of division by which ana mœba becomes two is sometimes spoken of as death and propagation, but there is no death in the case. Both parts equally live, and either might with equal right consider itself the mother and the other as the daughter body; and, if there be any transmission of consciousness and individuality, it is alike to both. We have no reason for supposing that either of the bodies will eventually die while the other lives; for, so far as our observation enables us to predict, both will go on dividing continuously without death taking place in any part. To account for the loss of the property of perpetual existence in the many-celled organisms, we may observe that a division of labor has been established among the cells as their structure has become more complex; and we have the life-supporting or somatic cells, and the reproductive cells, the former of which perform their several functions and cease to live, while the latter retain the faculty of continuous division or multiplication, and continue to live as the seed of offspring. They could not lose these properties without risking the extinction of the species. Death could not be introduced as a normal liability of one-celled organisms, because the two functions are united; but, in more complex organisms where there is a division of function, it is possible and exists. The normal vital term of the somatic cells appears to be contingent on the completion of the faculty of reproduction.

 


NOTES.

T. Egleston, in a paper on the causes of decay affecting building-stones, especially mentions such causes as depend on the removal of an ingredient by decay or decomposition. He observes that dolomitic limestones, which in some regions, in the case both of the native ledges and of monuments, crumble to sand, owe their disintegration to the fact that they are to a large extent mixtures of true dolomite and limestone; and that the limestone, the most soluble portion, is dissolved and removed by percolated carbonated waters.

A tunnel is projected, to be bored under Gray's Peak, in the Rocky Mountains. It will be placed 4,441 feet below the summit of the mountain, will be 26,000 feet long, and will give direct communication between the valleys in the Atlantic slope and those of the Pacific side, with a shortening of some three hundred miles in the transmontane distances.

Dr. p. H. Dudley recently described to the American Institute of Mining Engineers two cast-iron car-wheels which a chemical examination had shown to be almost precisely the same in composition, but one of which was good, while the other was nearly worth-less, for its purpose. From this, it appears that the value of articles of iron and steel is largely dependent on other conditions than