TWO-OCEAN PASS. i 75 



Two additional facts should be noted before closing the chap- 

 ter. 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 spe- 

 cialization, 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 unincor- 

 porated. 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 prac- 

 titioners, 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. 



** 



TWO-OCEAN PASS. 



By BAETON WAEEEN EVEEMANN, 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 shal- 

 low 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 thou- 

 sand 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. 



