STORAGE OF FAT JN MUSCUL.\R TISSUE OF KING SALMON. 87 



is located here. The region is accessible to fisheries which depend upon the catch of 

 salmon below the cascades of the Columbia. The samples of this series were chosen 

 from the fisheries at the seining grounds on the Washington side about lyi miles below 

 Warrendalc. 



The third stage was chosen at the Frank A. Seufert's fishery at The Dalles, on the 

 Columbia. The fish wheels and seining grounds along the course of the Columbia 

 below the Celilo Falls furnish splendid opportunity for salmon which have run the 

 lower mountain course of the Columbia River through the cascades and through the 

 lower portion of the rapids of The Dalles. 



The spawning-ground stage was that on the Clackamas River, Cazadero, Oreg. A 

 United States fishery is located here. This is the most accessible, in fact, the only point 

 W'here spawning salmon can be had during the time of the year in which the field work 

 was done. 



DISTRIBUTION OF THE FATS OF THE SALMON MUSCLE AT TIDEWATER. 



At the mouth of the Columbia River the salmon have already ceased feeding and 

 the muscles have begun to show the first stages of change in the amount and distribu- 

 tion of the fats. This change is readily detected in the pink muscle, though not so in 

 the dark muscle. In the dark muscle the amount of fat is so great that one has no 

 adequate microscopic comparisons for showing the variations. But it is easy to con- 

 vince one on general comparisons that the storage of fat is even as great in amount 

 as when the salmon first cease to feed, as they do at some considerable time before this 

 locality is reached in the migration journey. 



Trunk pink muscle. — In the trunk pink muscle the most striking change consists in 

 the fact of the appearance of intramuscular fat not noted previous to this stage. This 

 seems to be one of the first histological evidences of the cessation of feeding. At this 

 time the central core of the pink muscle fibers, and especially of the smaller fibers, is 

 dotted through with extremely small fat droplets. These fat droplets are rarely as 

 much as 2 // in diameter. Usually not more than i [i, and from this size down to droplets 

 so small as to be scarcely visible by the 1/12 oil immersion. All evidence that I have 

 points to the fact that this microscopic salmon fat reacts uniformly to the Herxheimer 

 stain whether the droplets be large or small. The pink muscle fat at this stage is quite 

 evenly distributed through the cross section of a fiber except in the outer circle of 

 fibrillae. In this circle there is no intramuscular fat. This gives the fibers the appear- 

 ance of having a clear surface border as distinguished from the inner portion of the 

 fiber, which is of course slightly pink from the presence of stained fat. At this stage I 

 can distinguish a few small and scattered fat droplets between the sarcolemma and the 

 muscle substance. The intramuscular liposomes are largest in the smallest pink fibers, 

 usually from two to three times greater in diameter on the average than in the very 

 large fibers. 



The trunk pink fibers show the details of liposome arrangement best in teased 

 preparations. The liposomes are in short chains consisting of a few individual droplets 

 in each. At this stage the Jiposomes in the middle of the chain are largest and they 

 decrease quite uniformly from the middle toward each end. These chains are loaded 

 in the interfibrillar spaces. They are present only in certain, not all, spaces between 

 groups of fibrillae. The number of such spaces occupied by the chains of liposomes, 



