455 



river, in the upper waters, or from kelts, showed a desquamative 

 catarrh of exactly the same kind as that described in the stomach, 

 intestine, etc. In some the epithelium had entirely disappeared, while 

 in others part of it could be seen in a degenerated state, either lying 

 detached in the lumen of the bladder, as was more usual, or attached 

 in fragments to the wall. There is no stratum compactum in the 

 gall-bladder; the connective tissue was in a state of more or less 

 evident hyaline degeneration. 



Conclusions. 



We may take it for granted that at some period of its existence 

 the salmon's alimentary tract has the same normal structure as that 

 of the trout, and it is evident that its sojourn in the sea is the time 

 of normal digestive activity. Probably for some time before the fish 

 enter the river, and certainly while they are lying at the mouth of 

 it, the catarrhal change begins, and begins clearly in the intestine 

 and pyloric appendages; the stomach is at that time unaffected. By 

 the time the fish have reached the upper waters the stomach has been 

 attacked, and the whole digestive tract is in a state of catarrh. After 

 spawning is over, the stomach is the first part to recover, and in the 

 kelts it is again histologically normal, while the intestine and pyloric 

 appendages probably recover when the fish have returned to the sea. 



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. The catarrh is probably associated with the general state 

 of nutrition of the fish. 



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 examin- 

 ation. 



Literature. 



1) Valatoue, M., Recherches sur les glandes gastriques et les tuniques 

 musculaires du tube digestif dans les Poissons osseux et les Batra- 

 ciens. Ann. des sc. nat., 4. Ser., Zool., T. 16, 1861. 



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

 logie des Tractus intestinalis der Fische. Inaug.-Diss. Bonn, 1883. 



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

 L Teil. Der Magen. Jena 1896. 



4) MiESCHER-RuESCH , Statistische und biologische Beiträge zur Kennt- 

 nis vom Leben des Rheinlachses im Süßwasser. Internat. Fischerei- 

 Ausstellung zu Berlin. Metzger und Wittig, Leipzig 1880. 



