FAT-ABSORBING FUNCTION OF ALIMENTARY TRACT OF KING SALMON. 1 59 



A series oi artificial feeding experiments was executed at the Hopkins' Seaside 

 Laboratory, followed by a more extensive series at the Federal salmon hatchery at 

 Baird, on the McCloud River in northern California. In this later series the question 

 of absorption in relation to the time following the administration of oil was especially 

 investigated. Furthermore, in the Baird series it was possible to maintain the young 

 fish without food an adequate time to insure the complete elimination of the fat from 

 the alimentary canal which might previously have been derived from natural foods. 



The Monterey series consisted of two salmon of the 2-year-old group with confirma- 

 tions on two salmon of the small i -year-old group, with different time allotments for 

 absorption, ranging from 20 to 70 hours. Careful examinations were made extending 

 over the stomach, intestine, and various pyloric coeca of each of these series. 



gener-AlL relations of the organs of absorption. 



The critical regions for the study of the absorption of fat in the salmon are three, 

 namely, the stomach with its two divisions, the cardiac and the pyloric ends; the intestine 

 with its two great divisions, the pyloric and post pyloric; and the numerous pyloric 

 coeca which have their origin from the pyloric intestine. 



These great divisions are of necessity to be described separately. Logically, one 

 might take them in the order, stomach, intestine, coeca; but because of the way in which 

 the evidence was accumulated and other questions attached to the subject it is more 

 convenient to discuss the details in the reverse order, i. e., absorption in the pyloric 

 coeca, in the intestine, and in the stomach. 



ABSORPTION OF FATS BY THE PYLORIC CCECA. 



The gross anatomy and the normal histological structure of the alimentary tract 

 of the king salmon have both been presented in a previous paper. " Figure i of that 

 paper is an illustration showing the general relations of the coeca to the pyloric end of the 

 intestine from which they arise in such profuse numbers. Those cceca which originate from 

 the beginning of the intestine, that is, in the neighborhood of the pyloric valve, are much 

 longer than those that arise from the posterior end of the series. These coeca often reach 

 a length of from 10 to 15 centimeters and even more in the adult feeding salmon. They 

 have a normal diameter of 5 to 8 millimeters. In the sea salmon taken at a time when 

 food is abundant and digestion has been going on actively for some time the coeca are 

 always gorged with material and distended to their full length and diameter. 



The content of the pyloric coeca under these conditions is peculiar in appearance. 

 One never finds solid particles of food. Instead, there is only, as Gulland and others 

 have mentioned, a creamy, yellowish, puslike mass which has a viscid adhesive con- 

 sistency. This content is never very fluid, i. e., of limpid character. The exact color 

 of the contents varies with the class of food material which the salmon is digesting at 

 the time. If the food is made up of Crustacea then the content of the coeca has a darker 

 color, often of a deep orange red. It is apparent that the viscidity of the mass is due 

 to the secretion of mucous by the epithelial lining of the coeca themselves. 



In the younger salmon the pyloric coeca have the same relative size, but of course 

 are smaller in proportion to the gross size of the fish. In no instance have I observed 



1 Greene, Charles W.. op. cit. 



