STORAGE OF FAT IN MUSCULAR TISSUE OF KING SALMON. I3I 



I have examined the pancreas of the king salmon for lipase, testing extracts of the 

 fresh normal glands of salmon caught in active stages of digestion. The experiments 

 were preliminary only, yet the tests were positive and the reactions vigorous. The salmon 

 pancreas secretes an active lipase. In my fat-absorption experiments there was always 

 a vigorous loading of the epithelial cells of the intestinal mucosa, especially in younger 

 fish. There was a greater mass loading than I have ever seen in mammahan intestinal 

 epithelium. This, by our current theories of fat absorption, is as strong circumstancial 

 evidence of the presence of lipase in the salmon mucous epitheUum as one could well 

 expect to discover. Aside from these tests no studies have been made on the lipases 

 of any of the Salmonidas. It is, of course, highly desirable that such studies should 

 be made. The amount and the variations of the lipase content of the salmon blood, and 

 especially of the muscles, should be determined by a series of quantitative tests. These 

 are the tissues of peculiar interest to the problem in hand. There are other tissues 

 directly concerned in the fat metaboUsms of the salmon — the liver, the divisions of 

 the alimentary tract, the pancreas, etc. 



However, on a priori ground, there is every reason for assuming that the salmon 

 is well suppUed with lipase in its fat metabolizing tissues, particularly in the alimentary 

 mucous epitheUum (the gastric epitheUum is also fat absorbing), the muscles, the Uver, 

 etc. The blood and the lymph can not escape a Upase content in an animal in which 

 so many of the tissues are concerned in the lipolytic processes. 



In previous discussions the conclusion has been reached that there is a marked 

 increase in lipolysis at the particular time the salmon cease feeding and begin the migra- 

 tion journey. This carries the assumption that there is at this time an increase in the 

 amount, i. e., percentage, of lipase in the blood and the tissues, including the muscular 

 tissues. Whence come these lipases? 



SOURCE OF THE LIPASES. 



The presence of a greater percentage of Upase when the cessation of feeding occurs 

 mav be explained on two physiological grounds, both of which are probably active; 

 first, there may be an absolute increase in the Upase produced in a given time; and, 

 second, it is possible that with the cessation of feeding the lipase that is usually con- 

 sumed in the intestine and pyloric cjeca in the processes of digestion and absorption 

 is now thrown more fully into the blood stream. To this extent it raises the percentage 

 content of lipase in the blood. 



The pancreas. — -The salmon pancreas is one proven source of lipase. The pancreas 

 is morphologically of the type described by Legouis " as the diffuse pancreas. The 

 gland filaments are quite separate from each other. They form an open meshwork 

 running over the pyloric caeca, the blood vessels and mesentery of the stomach and 

 intestine, the inner loop of the stomach, and the mesentery of the spleen. 



These pancreatic filaments are richly supplied with blood vessels, and these vessels 

 anastomose with the blood vessels of the caeca, intestine, etc., of the region. Pancreatic 

 ducts have been described by Legouis as converging to a common duct that enters the 

 intestine either with, or in the neighborhood of, the bile duct. 



<^ Legouis, P.: Recherches sur les tubes de Weber et sur le pancreas des poissans osseau. Annales des Sciences Naturelles 

 Zool., 5th ser., t. 17, 1873. See also t. 18, 2d article. 



