of the Salmon in Fresh Water. 



CHEMICAL CHANGES IN THE SALMON IN FEESH 

 WATER. 



PRELIMINARY CONSIDERATIONS. 



BY D. NOEL PATON, M.D., F.R.C.P. ED. 



It has been already shown that the salmon leaving its marine feeding 

 ground ascends the river and remains until the spawning time, often for 

 several months, without any supply of nourishment from without. 



During this period it must thus subsist upon the store of material in 

 its body brought from the sea. 



Hence a comparison of the condition of the salmon in the upper 

 reaches and in the estuary of the river at different periods will make 

 manifest the progress of the changes which go on in the fish during its 

 prolonged fast, and will explain how the material for the growth of the 

 genitalia and for the muscular energy required in the ascent of the 

 stream is obtained. 



The following sections deal with these matters : 



The question has been already investigated and discussed by Miescher 

 tluesch (loc. cit.), and before proceeding to give the results of the 

 present enquiry it is necessary to carefully consider his important 

 work. 



1. His investigations were practically confined to fish obtained in the 

 upper waters of a long river at the Basel-Laufenberg fisheries, about 

 500 miles from the mouth of the Rhine. 



2. His observations extended over three seasons, 1877 to 1880. From 

 the measurement and weighing of 470 salmon of from 840 to 917cm. in 

 length from May to November, he concludes that on an average the fish 

 loses about 6 per cent, of its weight from May 22nd to October 12th. 



3. From observations on 39 salmon he states that during this period 

 the ovaries increase from 1*1 percent, of the body weight to about 23 

 per cent. 



4. Analyses of the muscle in 15 salmon show that in the earlier part 

 of the year in July and August there is about 17-5 per cent, of 

 albumin (pro^eids), while later in November and December there 

 is only 13 per cent. He concludes that this loss of albumin alone from 

 the lateral trunk muscles is sufficient to cover four-fifths of the weight 

 of the full-grown ovaries. 



5. From the difference between the weight of the total solids and the 

 albumin he calculates the amount of fat in the muscle, and shows that in 

 August it is about 5 per cent, and in November about 2'2 per cent. 



6. To study the changes of material more accurately two salmon were 

 taken, one on the 7th and one on the 4th of August 1578, one an 



