449 



to be regarded as secretiog or absorbing organs. I think there can 

 be no doubt that, in the Salmonidae at all events, they fulfil the latter 

 function, for in structure they exactly resemble the upper part of the 

 intestine, so much so in fact that but for the difference in size it 

 would be impossible to say whether a section came from one or the 

 other. The digestive action which their contents have been shown, in 

 another part of this research, to possess, is probably due to the se- 

 cretion of the pancreas. The ducts of this organ appear to open into 

 the appendages, and its secretion would naturally impart to the con- 

 tents a digestive action. 



The intestine and appendages both have a peritoneal investment, 

 an external longitudinal and internal circular and thicker muscular 

 coat, no muscularis mucosae, a well-marked stratum compactum exactly 

 the same in character as that found in the stomach, a mucous mem- 

 brane thrown into longitudinal folds, and covered by a cylindrical 

 epithelium with the usual striated hem, and containing numerous chalice 

 cells (Figs. 5, 6). The only difference between the two organs is 

 that, generally speaking, the folds in the intestine are set more 

 closely together, so that the deepest parts of the folds look in sections 

 like short tubular glands or Lieberkiihnian follicles, whilst in the pyloric 

 appendages the folds are more open and there is no likelihood of 

 imagining the existence of glands at their bases. In both structures 

 the eosinophile leucocytes are numerous, but are to be found mainly 

 in the connective tissue about the stratum compactum. The leuco- 

 cytes in the folds and passing through the epithelium are usually 

 either of the hyaline or the smaller oxyphile variety. The epithelial 

 cells retain their striated hem (or fringe of processes, as it probably 

 really is), right down to the bottom of the folds. 



On opening either of these structures in the fresh state there is 

 always in the lumen a semi-fluid pultaceous mass varying in con- 

 sistence between jelly and pus, and more or less yellow in colour. 

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

 upper reaches, and from the sea. In the lower gut in this material 

 are numerous more opaque hard masses. These are composed of 

 large crystals of carbonate of lime held together by mucus. In none 

 of the very many specimens examined was the smallest trace of un- 

 digested food found in the intestinal tract. In the intestine of the 

 trout examined the remains of food were constantly present, and 

 appeared to consist mainly of parts of the exoskeleton and appendages 

 of small insects and crustaceans. In one case similar material was 

 found in the pyloric appendages, in other cases these were either 

 empty or merely contained entozoa. 



