of the Salmon in fresh Water. 19 



the intestines which contain thern there is nothing left but the muscular 

 coats, and a mere shred of connective tissue infiltrated with leucocytes. 

 But they are almost as common in the trout as in the salmon, and there 

 their presence does not produce a desquamative catarrh, but simply a 

 flattening out of the folds of the mucous membrane from distension ; the 

 epithelium remains intact. It is noticeable, however, that when these 

 worms are present in the trout the number of goblet-cells in the epithelium 

 is always unusually large, sometimes, indeed, the goblet-cells considerably 

 exceed the ordinary epithelial cells in number, as if the irritation caused 

 by the presence of the worm necessitated a greater flow of mucus to 

 lubricate the surface of the mucous membrane. 



THE PANCREAS. 



This is not gathered into a compact organ, but the acini are scattered 

 more or less diffusely through the long strands of intraperitoneal fat 

 lying round the stomach, pyloric appendages, and intestine (Fig. 14). The 

 microscopic ducts one can hardly call them interlobular or intralobular, 

 as there are no true lobules are lined with a cylindrical epithelium, and 

 resemble the ducts of mammalian salivary glands much more than those 

 of the mammalian pancreas. The cells of the secreting acini are like 

 pancreas-cells elsewhere, and they evidently go through exactly the same 

 cycle of appearance during the formation of and extrusion of zymogeii 

 granules as those described by Langley. One point of difference there is, 

 however, inasmuch as in the trout and salmon the zymogen granules in the 

 pancreas, as in the stomach cells, stain a deep black with iron-h?emat- 

 oxylin, which renders it very easy to make out the stage of secretion. 

 Fig. 1 5 shows a pancreatic acinus where the cells are full of granules, the 

 so-called stage of " rest," when no extrusion of granules is going on, 

 but where they are being heaped up in the cell ready to aid the process 

 of digestion. Fig. 16 depicts an acinus where the granules have mostly 

 been extruded, the so-called " active " stage. The only pancreas where 

 I found the cells completely full of granules was that of a trout which 

 had been preserved immediately after death. All the other trout and 

 all the Berwick salmon showed the cells more or less emptied of granules. 

 The pancreas was not often present hi the portions of salmon from the 

 rivers fixed for examination, but where it was to be seen the cells were 

 generally shrunken and shrivelled, and contained no granules. 



THE LIVEK. 



Comparatively few livers were examined, and these showed no very 

 marked difference beyond the presence or absence of fat. This is brought 

 out better, however, by chemical analysis (p. 100) and need 

 not here be discussed. Generally speaking, however, it was found 

 that the livers of the salmon taken at the river mouths contained much 

 fat (Fig. 18), while those of the salmon from the upper reaches, and the 

 kelts, were deficient in it (Fig. 1 7). The fat, where present, was generally 

 in the formof large droplets in the cells, and was distributed pretty 

 equally throughovit the organ. 



THE GALL BLADDER. 



The following are the statistics with regard to the state of the gall 

 bladder : 



