519 



occupies the lumen of the intestine is frequently found in some of the 

 appendages, but just as often nothing of this sort is observed save that 

 the epithelial lining exhibits a yellow tinge of bile. 



3) The micro-structure of the walls of the Gut. 



I do not purpose in this paper to give an account of the structure 

 of the walls of the gut, but merely to refer to those parts which are 

 implicated in the changes brought about by the different conditions to 

 which the salmon is exposed during its migration. 



a) The epithelium of the Gut. — Dr. Gulland affirms that 

 the whole lining membrane of the gut undergoes a desquamative 

 catarrh. This catarrh begins in the pyloric appendages and intestine, 

 and afterwards extends to the stomach. »On opening either of these 

 structures (i. e. the appendages and intestine) in the fresh state«, he 

 says, «there is always in the lumen a semifluid pultaceous mass varying 

 in consistence between jelly and pus and more or less yellow in colour. 

 This is the case alike is the salmon from the river mouth, from the 

 upper reaches, and from the sea. . . . On microscopic examination of 

 the appendages and intestine of the salmon«, he continues, »it is 

 found that the pus -like material is due to a desquamative catarrh 

 exactly like that found in the stomach. The mass in the tube is made 

 up mainly of rounded cells staining deeply with eosin, and having their 

 nuclei rounded, somewhat varying in size, but always staining deeply 

 and uniformly with haematoxylin . . . The main mass of cells is certainly 

 derived from the degeneration of the columnar epithelium which in 

 these cases is shed almost entirely from the folds of the mucous 

 membrane. ... I have never found a salmon in the intestine and pyloric 

 appendages of which (for the two are always at the same stage of the 

 process, another proof of their identity in function) this change was 

 not present to a greater or less extent ... In all fish from the higher 

 reaches, from the sea, and in the kelts from the river, the change was 

 complete. It is very curious to see the connective tissue frame-work 

 of the folds, with its bloodvessels much congested as a rule, lying 

 absolutely bare of epithelium in this pus-like mass«. 



Dr. Gulland further finds that the same catarrhal changes aflfect 

 the gastric epithelium, in which case the superficial cells are the first 

 to be cast ofi". 



As the results of prolonged investigations , in absolutely no case 

 have I found any trace of such desquamative catarrh of the mucous 

 membrane of the gut. The whole process as described by Dr. Gulland 

 is due to post-mortem changes as I have found on trial. He evidently 

 has not been able to obtain his material in a suitable condition — a 



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