of the Fishery Board for Scotland. 



37 



THE HERRING. 



I made extracts of the ' cardiac sac ' or ' crop ' by means of glycerine, 

 dilute spirit, chloroform water, and a solution of hydrochloric acid (2 per 

 1000). In all cases a strongly 'peptic' extract was obtained. In the 

 case of the glycerine extract the peptic action on fibrin was obtained 

 whether the mucous membrane was or was not previously treated with 

 alcohol. A flake of fibrin placed in a mixture of hydrochloric acid (2 in 

 1000), along with a proper amount of any of the above extracts, is 

 rapidly dissolved at a temperature of 37°-40° C, and much more 

 slowly at the ordinary temperature of the room. "When the solution of 

 the enzym is boiled no digestion takes place. As far as my experiments 

 go, I think the spirit extract is more powerful than that obtained by 

 chloroform. 



Instead of using fibrin as the proteid for testing the peptic action of the 

 extract of the cardiac sac, in several cases I washed and neutralised the 

 partially-digested contents of the crop of such herring as contained food. 

 These contents, whether crustaceans or sagitta, were also rapidly digested. 

 I made several experiments with other acids, such as lactic (1 per cent.), 

 and a similar result was obtained. 



It is therefore quite certain that the mucous membrane of the cardiac sac 

 or ' crop ' of the herring contains an enzym or ferment which is active in the 

 presence of an acid medium, and this ferment is pepsin, which in all 

 respects is identical with the pepsin of mammals. Krukenberg has 

 ascertained that pepsin exists in the stomachs of many fishes. 



The part of the cardiac sac which lies above the entrance into the so- 

 called ' stomach,' when acted upon by similar extracting reagents, also 

 yields pepsin. This is what one would expect from the histological char- 

 acters of the mucous membrane in this situation. 



The ' Pyloric sac ' or ' Stomach,' when similarly acted upon, yielded an 

 extract, with distinct, although feebler, peptic properties ; so that it also 

 contains pepsin. My experiments lead me to believe that the extract 

 of the mucous membrane of the pyloric sac is not so powerful as that 

 obtained from the cardiac sac. I have not made accurate experiments, 

 and compared the amount and potency of the ferment (pepsin) obtained 

 from these two organs ; but simple digestive experiments show that, other 

 things being equal, the extract of the pyloric sac does not digest fibrin so 

 rapidly as the extract of the cardiac sac. 



The Pyloric Appendages. — The uses and homologies of these 

 organs in fishes have for long been a subject of discussion amongst natur- 

 alists and physiologists. One point is quite certain — viz., that they seem 

 to subserve different functions in different fishes. To give a correct 

 exposition of their functions in any one species would require more 

 extended observations than my opportunities have afforded me. They 

 may be either absorbing or secreting organs, or both. The question as 

 to their absorbing function must rest upon what facilities are afforded to 

 the chyme for entering these organs in the different species, and also 

 upon their structure. In some fishes, as Krukenberg has pointed out, 

 they are purely mucous glands (Perca fluviatilis) ; whilst in others they 

 represent the pancreas, i.e., they contain a 'tryptic' ferment (Clupea 

 Sardinia). Some of the older observers regarded the pyloric appendages 

 as true absorbing organs, and nothing more, a view which was partly 

 supported by Rathke,* Meckel,! and more especially by Edinger,J who, 

 however, supports his view entirely from histological observations. In 



* Miiller's Archiv, 1837, p. 354. t Anatomic Coviparee. 



X Archiv f. Mik. Anat., vol. xiii. p. 651. j 



