of the Salmon in Fresh Water. 29 



1 . FISH FROM THE ESTUARIES. Of the 23 fish caught at the mouth 

 of the rivers the glycerine extract of the gastric mucous membrane 

 possessed some peptic power in 15. The average percentage of 

 albumin digested in these is ] 4-6, while check experiments with 

 ordinary commercial pepsine, at the ordinary temperature and with the 

 same proportion of hydrochloric acid, show a digestive power reaching 

 to 72 per cent. Including all the fish caught at the mouth the 

 digestive activity only equals 9 -5 per cent. 



2. FISH FROM THE UPPER WATERS. Four of the five fish from 

 the upper waters were found to give positive results in this part of the 

 research, with 11-8 per cent, of albumin digested. The total number 

 five give a percentage of 9- 17 per cent. 



These results seem to indicate that the mucous membrane of the 

 stomach in the fish which have reached the upper waters of the rivers 

 possesses a somewhat smaller peptic power than that of salmon caught 

 close to the sea. 



3. KELTS. The figures obtained from the four kelts show a higher 

 digestive activity than in the fish included in the first and second 

 classes namely, 22-7 per cent. One of the kelts, however, possessed no 

 proteolytic ferment in its stomach ; the remaining three possessed a 

 digestive power of 2 9 -8 per cent. The kelt without digestive power was 

 one which had not returned to the sea in July. 



(b) Relation of Peptic Activity to Acidity. 



A comparison of the percentage acidities of the extracts with their 

 proteolytic power shows a direct relationship between these, although 

 in several cases the relationship is departed from. In the fish 

 caught at the river mouths those in which an active digestion of 

 albumin w^as found, to a greater or less extent, the mean acidity of the 

 extracts of the stomachs reached 0*244 per cent, in terms of hydro- 

 chloric acid, against 0-023 per cent., or ten times as little, in those in 

 which 110 digestive action occurred. Similarly, of the five fish from 

 the upper waters the four presenting actual evidence of digestive 

 power give a mean acidity in their extracts of 0-074 per cent., the 

 remaining one a mean of only O'Ol per cent. 



In Table IV. the figures relating to the comparison between the 

 amount of albumin digested and the acidity of the extracts are given 

 for the total number of fish used : 



TABLE IV. 



RELATION BETWEEN THE DIGESTIVE POWER AND THE ACIDITY. 

 Totals. 



In the total number, 32, the digestive power averages 11-1 per cent., 

 the acidity 0-166 per cent. In the 22 with some actual digestive power 

 this reaches 16-13 percent., the acidity 0-231 per cent., while in the 

 10 fish in which no peptic digestion occurred the mean acidity is 



