of the Salmon in Fresh Water. 27 



3. METHODS. 



The stomach and intestine of each fish used for the purpose of testing 

 the digestive activity were placed, after removal, in methylated spirits 

 for forty-eight hours to extract the excess of fatty matter, and to 

 harden the tissues. They were then taken out of the spirit, cut up into 

 small pieces, and placed in glycerine, to which a small quantity of water 

 had been added. After a month to six weeks the glycerine extract was 

 filtered off, and made up in each case to 50 cc. The stomachs and 

 intestines were treated separately. 



The activity of the extracts was then determined in the usual way. 

 5 cc. of the extracts were added to 10 cc. of an egg-albumin solution 

 of known strength, hydrochloric acid or sodium carbonate mixed with 

 it, and the whole made up to 50 cc. by the addition of water. The 

 amount of hydrochloric acid added represented in each case the quantity 

 necessary to form an acidity of 0*1095 per cent, in the 50 cc., and the 

 sodium carbonate represented 1'5 per cent, in alkalinity. 



Of the solutions 5 cc. were used to estimate the acidity or alkalinity 

 present, and the remaining 45 cc. were left at the ordinary temperature 

 of the laboratory for six to eight hours. 



The solutions were then neutralised, boiled, and then acidified with 

 acetic acid, a few drops of a saturated solution of acetate of soda being 

 also added. The precipitate which formed was caught on a weighed 

 filter-paper, washed with boiling water, alcohol, and ether, and then 

 dried and weighed. The increase in the weight of the paper represented 

 the amount of albumin still undigested. This subtracted from the 

 original weight of the albumin employed gave the quantity digested. 

 Corrections were made in these figures for the amount of coagulable 

 proteid contained in the glycerine extract on several occasions at the 

 commencement of the research, but as the additional precipitate was 

 found to be so small, and to be practically constant, it has been ignored 

 throughout. 



The diastatic power of the glycerine extracts was estimated by its 

 action on starch, a solution of iodine and iodide of potassium being 

 employed as the indicator. A 1 per cent, starch solution was made 

 faintly alkaline with sodium carbonate, 5 ccm. of the extract added, 

 and the mixtxire left for two hours at the temperature of the room. 



No action was obtained from the gastric extracts, and the further 

 details of the experiments with these extracts are omitted. All the 

 intestinal and appendicical extracts proved to be fairly active. 



4. DIGEST ON IN THE STOMACH. 



() The Peptic Activity of the Glycerine Extracts of the Gastric 

 Mucous Membrane. 



In Table III. the details of this part of the research are sum- 

 marised : 



[TABLE. 



