FAT-ABSORBING FUNCTION OF ALIMENTARY TRACT OF KING SALMON. 171 



THEORETICAL CONSIDERATIONS. 



The observations detailed in the preceding pages made on adult normal feeding 

 salmon and on younger specimens under artificial and experimental feeding of fats 

 show beyond doubt that fat is absorbed by all portions of the alimentary tract. The 

 food of the salmon, which is representative of the carnivorous fishes, is made up of 

 living organisms. These are wholly marine forms during adult life and are represented 

 by the crustacean, molluscan, and piscatorial forms. All these classes of animals 

 possess a high percentage of fat in their tissues, particularly the fishes, which form so 

 large a portion of the salmon foods. Fats, therefore, form a large percentage of the 

 normal food substance for the king salmon. The importance of this food material needs 

 no further emphasis. The question at issue in this paper, therefore, is that of the ability 

 of the salmon to digest and absorb the fatty elements so rich in quantity in its foods. 



It is of vital significance that the fats are digested and absorbed in all the great 

 divisions of the alimentary canal. It is true that fat digestion as such has not been 

 followed in this series of experiments, but much collateral evidence has been obtained, 

 and certain experiments not reported have shown something of the digestive process. 

 Of all the observations the most important would seem to be the establishment of the 

 fat-absorbing function of the pyloric cceca on the one hand and, on the other, the fact 

 that fat is absorbed in the stomach. 



As regards the pyloric coeca, the function of these organs has previously been 

 deduced rather than proven by scientific experiment. Cuvier, at the beginning of the 

 nineteenth century, considered the cceca as pancreas. At a still earlier date the general 

 theoretical view was advanced that the cceca had to do with absorption. In more 

 recent times statements have been advanced that the cceca are concerned with diges- 

 tion and absorption. Of course, in an}' division of the alimentary tract it is a safe 

 assumption that the function has to do either with digestion or absorption of some 

 one or more of the food principles. 



So far as I can find, no one has, previous to my experiments, attempted to demon- 

 strate the relation of the pyloric cceca to fat digestion and fat absorption. The preced- 

 ing obser\'ations establish beyond further doubt that the pyloric coeca are primarily 

 fat absorbers. Incidental observations indicate that fat digestion may and does take 

 place in these organs as shown further in m}- first publication of facts from this inves- 

 tigation. "^ 



The second important obser\'ation, that of the fat-absorbing power of the stomach, 

 is also of great physiological significance. As was indicated in the introductory dis- 

 cussion of the literature, the fact that fats are digested and absorbed in the stomach 

 has been established previously by work on mammals. Strange to say, this work has 

 been largely overlooked or for one reason or another questioned, so that the full accep- 

 tance of fat digestion and absorption by the stomach has not even yet been granted. 

 Van Herwerden first showed fat absorption by the stomach in fishes. Following the 

 publication of my preliminary report,* Weiss'^ published a brief report on experiments 

 showing the absorption of fats by the stomach of the snake. Emphasis was laid on 

 the fact that the fat absorption takes place more readily in the young than in the adults. 



« Greene, op. cit. f* Idem, op. cit. c Weiss, op. cit. 



