PHYSIOLOGICAL STUDIES OF THE CHINOOK SALMON. 



By CHARLES WILSON GREENE, 

 Professor of Physiology, I 'niversity of Missouri. 



I. RELATION OF THE BLOOD PRESSURE TO THE FUNCTIONAL ACTIVITY. 



INTRODUCTORY. 



The salmon is an anadromous fish. Its natural spawning beds arc in the cold 

 waters of the mountain streams. When the eggs are hatched and the young are able 

 to swim, they proceed down the streams and out into the open ocean, where they 

 feed and grow for a period of two to four years. On the approach of maturity they 

 reenter the mouths of the rivers and make the long journey back to the spawning 

 grounds in the mountain waters, a distance sometimes of hundreds of miles. The 

 mature salmon as they approach the mouths of the rivers are strong and vigorous 

 and in the very prime of condition. They have been feeding voraciously on the 

 abundant ocean fauna and their tissues are loaded with the supply of fats and oils and 

 other constituents which make the flesh so much sought after because of its delicious 

 flavor and nutritious excellence. 



The fact which presents so peculiar and interesting a problem, or series of prob- 

 lems, in fact, to the physiologist is this: The salmon takes no food after it leaves the 

 ocean and enters fresh water." The journey, it may be of hundreds of miles, is made 

 against the swift currents, rapids, and waterfalls of the mountain streams. It matters 

 not how long the distance nor how great the exertion that is required, all the energy 

 must be supplied from the store of material accumulated while the fish is feeding in 

 the ocean, material present in its body when it enters the fresh-water stream. 



A prolonged fast is always of especial physiological interest. The winter sleep 

 or hibernation of the bats, dormice, and the bears, while it is a period of fasting, is 

 also a period of inactivity. All the vital processes are reduced to a minimum and 

 little energy is liberated. In the salmon, on the contrary, the fasting period is the 

 period of the greatest activity of the fish's life. The changes and reactions within 

 the body of an animal that is giving off daily a large amount of energy, and at the 

 same time is taking in no food to renew its vitality, present peculiar physiological 

 phenomena. Nature herself performs the experiment of inanition in the salmon and it 

 remains for science to unravel the details. The main question is how long and through 



<iThis statement is borne out by the researches of the Bureau of Fisheries, and investigations by Mieschcr-Ruesch and 

 Noel l'aton on the Atlantic salmon in Europe show the same to be true of that species also. 



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