24 Investigations on the Life-History 



Krukenberg (Untersuchungen aus dem phys. Instit. der Univ. Heidel- 

 berg, 1882, II., p. 396) states that the pepsine of the stomach of fish, 

 or an analogous body to pepsine, acts as well at 20C. as at 40C., 

 and is most powerful in solutions of hydrochloric acid containing 1, 

 1-5, or 2 grammes per litre, but is active in solutions with 10, 15, or 

 20 grammes of this acid in the litre. 



The frequent absence of the remains of food in the stomach of feed- 

 ing fish very shortly after its ingestion led some to the idea that the 

 rapidity of digestion might be accounted for by the action of the bacteria 

 in the stomach in assisting the gastric ferment, or might even be due 

 to the unassisted action of the bacteria. 



Richet, however, has showed (loc. cit.) that an extract of the gastric 

 mucous membrane of fish is capable of digesting albumin in a 2'3 per 

 cent, solution of hydrochloric acid, and in the presence of ether or 

 chloroform in excess, or of cyanide of potash. Under none of these 

 conditions would bacteria be able to exist. 



In herbivorous fish, such as the carp and tench, a diastatic ferment is 

 present in the gastric secretion. In carnivorous fish this ferment is 

 absent. 



In 1880 Miescher Ruesch published an important paper founded 011 

 his observations on the physiology of salmon caught in the Rhine during 

 the preceding eight years. He agreed with Barfurth, His, and Glaser, 

 that " the Rhine salmon takes no food from the time when it leaves 

 the sea until it has spawned, and seldom even after this," until it again 

 reaches the salt water. No remains of food were found by him in any 

 of the winter and spring fish examined. The mucus occurring in the 

 stomach was never acid in reaction. No active digestive ferment 

 seemed to be secreted, while a glycerine extract of the gastric mucous 

 membrane exhibited little proteolytic power. 



In a male fish, however, coming from the spawning beds a kelt he 

 found in a large, flabby stomach two fairly large fish whose anterior 

 portions were already digested. In another male kelt, although no 

 trace of food was present, he found that the thin secretion of the 

 stomach was of acid reaction. 



To sum up the outcome of Miescher Ruesch's work, it would seem 

 that salmon ascending streams to the spawning grounds do not feed, 

 and that if they swallow portions of food they are unable to digest 

 them. After they have spawned, the males occasionally take food on 

 their way down to the sea ; the female fish may or may not do so, but 

 Miescher Ruesch failed to find any evidence in support of this, while as 

 regards the male fish, the gastric glands have become so far more active 

 that their secretion possesses an acid reaction. 



2. THE MATERIAL EXAMIXED. 



In Table I. the details regarding the date of capture, the part of the 

 river from which the fish were obtained, the number of fish used for 

 investigating the peptic and tryptic power of their extracts, and the 

 total number of salmon employed are arranged in tabular form : 



[TABLE. 



