136 BULLETIN OF THE BUREAU OF FISHERIES. 



RESUME. 



The points made in this investigation that call for special mention may be cate- 

 gorically stated as follows: 



1. Fat' is the prominent and immediate source of the energy of the salmon 

 expended during the spawning migration. 



2. The salmon fat is stored in the body during the stage of feeding and growth, 

 and reaches a maximum at the time the feeding stage ends, i. e., at the beginning of 

 the migration fast. This fat can not in any proper sense be looked upon as a fatty 

 degeneration. 



3. The fat storage tissues are primarily the muscles and intermuscular connective 

 tissues. Storage tissues of minor importance are the cutaneous and other adipose 

 tissues, the liver, the alimentary tract, and the skeleton. 



4. There are two distinct and characteristically different types of muscle — the 

 superficial lateral or dark and the deep lateral or pink muscle. The latter represents 

 the major portion of the great lateral muscle mass. 



5. The pink muscle is characterized (a) by the enormous load of fat between the 

 fibers, intermuscular fat, and in the myocommata at the time of maturity; (6) by the 

 great variation in the size of its fibers. 



6. The pink muscle fibers have no intramuscular fat, or at most only traces of fat, 

 during the feeding stage. 



7. Immediately at the beginning of the spawning migration the pink fibers are 

 loaded with numerous chains of very small liposomes. This loading of liposomes 

 increases during the early stage in the journey, and then decreases somewhat up to the 

 spawning time. The fat never wholly disappears even in dying salmon. 



8. In the active caudal pink muscle the liposomes are much less constant and are 

 often completely absent as advanced stages of exhaustion appear. 



9. The pink muscle fibers are plump and cylindrical at the time the migration 

 begins. But at the spawning time the larger fibers have the appearance of being 

 shrunken by decrease in mass. They become polygonal in cross-sectional outline. 

 The sides of the polygon are often concave to the exterior, as if compressed by the 

 adjacent smaller fibers. 



10. The dark muscle is characterized (a) by the enormous loading of intramuscular 

 fat at all stages of the life cycle, but especially at the time the spawning migration 

 begins; (b) by the relatively small and uniform size of the fibers. 



1 1 . The stored fat of the dark muscle is gradually eroded during the migration 

 until the fat reaches a quantity and distribution comparable to but still greater than 

 that in the pink fibers. The fat is never completely eroded and is present in considera- 

 ble quantity at the death of the salmon after spawning. 



12. The smaller muscles of the fins and of the head of the salmon take little part 

 in the fat storing. The food supply of these muscles, however, is the same, namely, 

 the fats. 



13. Distinct degenerative changes were found in the adductor mandibulae muscle 

 of a spawned male at the dying stage. This degeneration is a simple atrophy with 

 pigmentation. 



