Page:Popular Science Monthly Volume 47.djvu/185

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175
TWO-OCEAN PASS.

Two additional facts should be noted before closing the chapter. One is the recent differentiation by which certain professors of anatomy and physiology have been made into professors of biology. In them the study of human life has developed into the study of life at large. And it is interesting to see how this specialization, seemingly irrelevant to medical practice, eventually becomes relevant; since the knowledge of animal life obtained presently extends the knowledge of human life and so increases medical skill. The other fact is that along with incorporation of authorized medical men there has arisen jealousy of the unincorporated. Like the religious priesthood, the priesthood of medicine persecutes heretics and those who are without diplomas. There has long been, and still continues, denunciation of unlicensed practitioners, as also of the "counter-practice" carried on by chemists and druggists. That is to say, there is a constant tendency to a more definite marking off of the integrated professional body.


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TWO-OCEAN PASS.

By BARTON WARREN EVERMANN, Ph. D.,

ICHTHYOLOGIST OF THE UNITED STATES FISH COMMISSION.

IT was while the Great Ice King still ruled over all America from the pole to the middle United States that Lake Lahontan and Lake Bonneville spread their waters over hundreds of square miles of our western territory; Lahontan where we now have the sage plains and alkali sinks of Nevada, and Bonneville covering the greater part of Utah west of the Wasatch Mountains, but now reduced to Sevier, Utah, and Great Salt Lakes, the last shallow remnants of a once mighty inland sea. It was probably long before these great lakes had dried up, while their waters were yet fresh and sweet, that occurred an event which wrought a vast change in the physical geography of that region. Somewhere, but no one is yet certain exactly where, one or more great fissures opened in the earth, and there poured out an incredible amount of lava which covered not less than one hundred and fifty thousand square miles with one vast sheet of rhyolite hundreds, in some places thousands, of feet in thickness. Northern California, northwestern Nevada, nearly all of Oregon, Washington, and Idaho, and parts of Wyoming, the Yellowstone Park, Montana, and British Columbia were all covered by this stupendous flow.

The effect of this lava flow upon the present distribution of the fishes of that region is known to have been very great, and we are now beginning to understand some of the most important factors of that distribution — a distribution which, until recently, presented many anomalies.