96 NOTES AND COMMENTS [febeuauy 



Do Salmon feed in Fresh Water? 



In the Report of Investigations on the Life-History of Salmon (Fishery 

 Board for Scotland, 1898), edited by Dr. Noel Paton, there are two 

 papers — by Dr. G. Lovell Gulland and by Dr. A. Lockhart Gillespie — 

 which bear directly on the long-dispnted question whether salmon feed 

 while in fresh water. The Edinburgh workers agree with Miescher- 

 Eeusch (1880) in answering the question in the negative, thus differing 

 from a well-known Scottish authority — Prof. W. C. MTntosh. The 

 evidence adduced in the Eeport is threefold : — (a) During the salmon's 

 stay in fresh water the mucous membrane is in a state of desquamative 

 catarrh which suggests a cessation of function. This is corroborated 

 by the absence of zymogen granules in the pancreas, the fatty condition 

 of the liver, the emptiness of the gall bladder, and the absence of all 

 trace of food. (b) Experiment showed that the proteolytic and 

 diastatic action of the digestive secretions was extremely low. (c) The 

 number of bacteria in the gut is very great, especially during the warm 

 months, and this is interpreted as probably due to the diminished 

 acidity of the gastric fluids. This is, of course, merely a hint of the 

 nature of the actual evidence, which seemed to us so convincing, when 

 we first read it, that we were rash enough to think that the question 

 was settled at last. 



It seems that this is not so. In a paper in the Zoologisclier 

 Anzeiger, 1898, xxi. pp. 514, 515, 517-523, Dr. Alex. Brown, 

 Lecturer in Zoology in the University of Aberdeen, who has had great 

 facilities in studying salmon, maintains that though the river fish are 

 not in a condition to feed voraciously as in the sea, they do feed 

 occasionally, much depending on external conditions, such as the 

 temperature, density, and volume of the water. He does not find any 

 trace of the catarrhal conditions observed by Dr. Gulland, except as. 

 the result of post-mortem changes ; but he finds microscopic foreign 

 particles and crystals of carbonate of lime in the intestine, which are the 

 indigestible remains of ingested food. Moreover, the presence of leucin 

 crystals in abundance and of tyrosin in the intestine point to the 

 decomposition of proteid by the pancreatic juice ; and the pyloric and 

 intestinal contents have a strongly active digestive character. Two 

 more contradictory sets of results it would be hard to find ; and we 

 look with eagerness for a reply from the Edinburgh laboratory. It is 

 difficult to believe that an expert histologist was deceived by post- 

 mortem changes. 



None of the investigators have as yet thrown light upon the fact 

 that the salmon, alleged to be fasting, will still rise to the fly, or 

 accept a prawn. We suspect that the explanation will be found to be 

 psychological rather than physiological. 



