515 



1) When salmon leave the sea they have in their bodies a supply 

 of nourishment not only sufficient to yield the material for the growth 

 of ovaries and testes, hut to afford an enormous supply of enero;y for 

 the muscular work of ascending the stream. 



2) During the stay of the fisli in fresh water the material accumu- 

 lated in the muscles steadely diminishes, and there is absolutely no 

 indication that its loss is made good by fresh material taken as food. 



3) The functionless condition of the whole gut, due to a desqua- 

 mative catarrh of the mucous membrane. 



4) The low digestive power of extracts of the mucous membrane 

 of the stomach and intestine not only in upper-water fish but in fish 

 approaching the river mouth, indicating that the salmon has practi- 

 cally ceased to feed before it makes for the estuary. 



5) The greater abundance in upper- water fish of putrefactive 

 organisms which are most readily destroyed by free acids. This 

 would indicate m the upper-water fish the absence of the free acid 

 which is formed in the stomach of fish during digestion, and which if 

 ])resent would destroy them. 



6) The absence of food or undigested remnants of food in the 

 stomach and intestine. 



On a careful examination of these alleged facts, it avìU be seen that 

 the evidence for the nonfeeding of salmon in rivers to a very large 

 extent rests with (3). It seems to me that the whole question can be 

 ]iractically settled by a careful study of the digestive and absorptive 

 surfaces of the gut and of the seasonable changes there observable. In 

 the present paper then, I wish to give a brief account of the results 

 of my investigations on the histological characters of the gut of the 

 salmon in so far as they bear on the question at issue. 



For histological work on the alimentary canal it is absolutely 

 necessary to obtain the material in a perfectly fresh condition imme- 

 diately after the capture of the fish. Every part of the gut to be 

 examined must be opened up and placed at once in the fixing fluid, for 

 I have found that post-mortem digestion occurs particularly in the py- 

 loric appendages and intestine in from 30 to 45 minutes after death. 

 To post-mortem digestion, as will be shown later, is due the existence in 

 the pyloric appendages of the pultaceous, creamy-like substance refered 

 to by Fritsch^', Miescher- Reusch ^^ Gulland^ and others. 



(Schluß folgt.) 



5 Ant. F ritsch, Der Elbelachs p. 96. 

 •5 Loc. cit. 



• Gulland, Rep. Investig. Life Hist, of Salmon Fish. Board Scotland. 1898. 

 p. 16, 17. 



