TEE BREEDING SALMON. 509 



ported by the thorough investigation of Dr. Noel Paton and his co- 

 workers of the Scottish Fishery Board on the salmon of their rivers. 

 They have determined the amount of the various fuel materials which 

 disappear from the bodies of the salmon during their journey up 

 stream. For this purpose they have analyzed all the tissues and organs 

 of numerous salmon taken from the estuaries in the spring and early 

 simimer, just as the fish were starting up the rivers. They also found 

 the amount of fat and albuminous material remaining in the tissues 

 of the fish taken from the head waters of the rivers, a month or so 

 later. By calculating from the numerical results of these analyses 

 the equivalent figures for a fish of 'standard length' — arbitrarily taken 

 at one meter — a fairly accurate basis of comparison was obtained. On 

 this basis the difference in the composition of the tissues of the fish 

 of the estuaries, and those of the head waters, reveals the number of 

 grams of fat and albuminous material which the journey up stream 

 costs the fish. The results show that, varying with the length of their 

 journey — which in no case approaches the distance up the Rhine — 

 the swiftness of the current overcome, and the other exertions necessary, 

 the salmon in passing from the estuaries to the head waters, expend 

 three hundred to six hundred grams of fat, and only sixty to a hundred 

 and twenty grams of albuminous material. In the animal body the 

 combustion of the fats and sugars is complete. They leave the system 

 in the form of carbonic acid and water, after liberating within the 

 tissues precisely that amount of energy which they would yield as heat, 

 if burned in a perfect lamp or the most accurately constructed calorim- 

 eter. For the albuminous substances the combustion is less complete; 

 but the amount of energy which comes from each gram decomposed 

 within the body is determinable with no less accuracy than for the 

 fats. To find the energy which the salmon expend in the ascent of the 

 Scottish rivers, it is only necessary, therefore, to multiply the amount 

 of fuel material expended by the number of calories which one gram 

 of fat or albuminous material yields in a calorimeter. Thus it is 

 found that the same six hundred grams of fat and one hundred and 

 twenty grams of proteid, which the journey up the longer rivers costs 

 the salmon, would heat sixty-five liters of water from the freezing 

 point to boiling, or, to express the same amount in terms of mechanical 

 ^ork — would, if theoretical conditions in this regard were attainable, 

 lift fourteen kilos (the weight of the 'standard fish' of the Scottish 

 investigations) to the height of a hundred and eighty kilometers. But 

 it must be borne in mind that the dynamic efficiency of few engines 

 devised by man exceeds fifteen per cent.; and the investigations of 

 physiologists have shown that the contracting muscles develop an 

 efficiency only five to ten per cent, greater. From such data as these, 

 together with the rate of flow of rivers, their length, and the time 



