of the Salmon in Fresk ll'ater. 



21 



It is evident that this desquamative catarrh is not caused by the 

 action of fresh water either on the general health of the fish or locally 

 on the parts of the alimentary canal, for in many fish taken from the 

 sea the change was already complete in the intestine and appendages. 



Finally, it is well again to emphasise the fact that in no part of the 

 alimentary canal of the many fish examined, including kelts, were any 

 remains of undigested food discovered upon microscopic examination. 



LITERATURE. 



1 . Valatonr M. Recherches sur les glandes gastriques et les tuniques 

 musculaires du tube digestif dans les Poissons osseux et les Batraciens. 

 Ann. des Sc. nat. 4. Ser. Zool. T. 16. 1861. 



2. Cajetan, J. Ein Beitrag zur Lehre von der Anatomie und 

 Physiologie des Tractus intestinalis der Fische. Inaug.-Diss. Bonn. 

 1883. 



3. Oppel, A. Lehrbuch der vergleichenden mikroskopischen Anatomie. 

 ler. Teil. Der Magen. Jena.. 1896. 



4. Jliescher. Fischerei-Ausstellung zu Berlin. 1880. 



DESCRIPTION OF THE FIGURES. 



The following letters are used to indicate the same structures through- 

 out : 



eosiiioplule leucocyte, 

 mucosa. 

 submucosa. 



epithelial part of mucous 

 me. 



superficial epithelium, 

 int. ep. , - intermediate epithelium, 

 zymin-secreting epithelium, 

 zymogen granules, 

 columnar epithelium, 

 chalice cell. 



degenerated epithelium, 

 pancreatic duct. 

 - fat. 



Figs. 1 to 6 are micro-photographs of actual sections ; the lens used 

 was Leitz 3 and ocular 4. The remaining Figures are drawings by the 

 author. The outlines were, in all cases, filled in with Zeiss's camera 

 lucida. For Figs. 8, 9, 10, 15, 16. 17, 18, the objective was Zeiss's 

 homog. immers., apochr. 2'0 mm., apert. 1'40 with compensat. ocular 8: 

 and the magnification is therefore x 1000; for Figs. 12 and 13, the same 

 objective, with compensat. ocular 4, magnification x 500 ; for Fig. 7, 

 Zeiss DD., with ocular 2, magnification about x 200; for Figs. 11 and 

 14, Leitz 3 with ocular 4, magnification about X 60. 



Fig. 1. Stomach of salmon from mouth of river (Berwick), showing 

 normal mucous membrane. Iron-ha?matoxylin. 



Fig. 2. Stomach of salmon from upper waters, showing early stage of 

 degeneration and desquamation, and hyaline change in connective tissue. 

 Iron-h?ematoxylin. 



Fig. 3. Stomach of salmon from upper waters, showing very advanced 

 stage of degeneration of the mucous membrane. Iron-haematoxylin. 



Fig. 4. Stomach of kelt, showing regenerated mucous membrane. 

 The secreting epithelium of the glands is loaded with zyniogen granules, 

 which are stained black. Iron-hrematoxylin. 



Fig. 5. T.S. Intestine of salmon from the mouth of river (the only 

 one where there was no catarrhal change), showing the folds of the 



