STORAGE OF FAT IN MUSCULAR TISSUE OF KING SALMON. 9 1 



The intramuscular fat is relatively small in amount. Many of the fibers show 

 liposomes of extremely fine size, often so small that one can trace them with difficulty. 

 There are no rings of fat droplets under the sarcolemma such as characterize muscle that 

 is beginning to show fat exhaustion. There are certain groups of fibers in these sections 

 which show a relatively larger amount of intracellular fat. In such fibers the liposomes 

 will average as much as 2 /< in diameter. The liposomes are quite evenly distributed 

 through the cross section of the fiber and are occasionally quite numerous under the 

 sarcolemma. This latter type pi fiber is suggestive of the dark muscle type. Not 

 enough comparative work has been done in studying these muscles to determine whether 

 or not the dark muscle fibers are present in portions of these muscles. There is some 

 indication that the superficial muscle of the anal fin, the inclinator analis, contains fibers 

 of the dark type, whereas the erector and depressor muscles are more nearly of the pink 

 type. If the inclinator contains fibers of the dark type it would suggest that that 

 muscle is more nearly homologous with the superficalis lateralis, a homology that needs 

 further investigation. 



Fat of the adductor mayidibulcE or cheek muscle. — The fibers of the muscle are more 

 compactly arranged and different in appearance from the other portions of the salmon 

 musculature. They are, however, most like the great lateral pink muscle. At Ilwaco 

 the intermuscular fat is distributed in scattered but relatively large fat droplets, 60 to 

 70 [1 in diameter. There is also a comparatively large number of small droplets not over 

 20 fi in diameter. 



The intracellular fat is always present. The large fibers in the muscle carry a few 

 scattered chains of extremely minute liposomes. On the other hand, the smallest fibers 

 have liposomes about 0.6 /z in diameter. 



Considering the muscle as a whole at the Ilwaco station the fat distribution is most 

 nearly like that of the great lateral pink muscle, though both the intermuscular and 

 intramuscular fat is very much less in quantity. This muscle, like the fin muscles, carries 

 a relatively small amount of intramuscular fat. This fat is more than adequate for the 

 uses of the muscle, but the striking fact shown by the sections is that there is never an 

 excessive accumulation of the fat. 



AN.'\LYTIC.\L DETERMIN'.^TIONS OF THE PERCENTAGE OF FATS IN SALMON FROM THE 



MOUTH OF THE COLUMBIA RIVER. 



When this study was projected it was planned to take a full set of samples of the 

 muscles studied and make fat determinations by accurate chemical methods. Such a 

 full set of determinations would have been very valuable in itself but of inestimable 

 value as corroborative evidence in connection with the microscopic comparisions. It 

 turned out to be impossible to carry through the full program of the work and the sacri- 

 fice fell on the chemical series. Chemical samples were taken, however, whenever it 

 could be done, though the analyses were reserved to be made not in the field but in the 

 home laboratories. The few samples secured were not analysed until after the micro- 

 scopic work was completed and the results sent off for publication. 



The fat determinations secured on samples from Ilwaco are inserted at this point. 

 Considering the fact that the eight Ilwaco fishes were chosen to represent the entire 

 range of types present in the lower Columbia at the time of the expedition, this showing 

 of fat percentages is most significant. The salmon were taken, first, from the main 



