STORAGE OF FAT IN MUSCULAR TISSUE OF KING SALMON. 99 



In the fatter specimen the largest fibers are relatively thickly filled with numerous 

 chains of Hposomes. These chains are more numerous than in fish no. 115 and no. 118 

 from Ilwaco, and the size of the liposomes in the chains is, if anything, comparatively 

 greater. When the poorest fish are examined, it is found that the large fibers are strik- 

 ingly low in fat, for example, no. 126, fig. 10, pi. vii. In fact, it is difficult to distinguish 

 liposomes in the largest trunk pink fibers of this fish. In numerous instances observed 

 there were tiny groups of very small liposomes ranged near the surface of the cell, chiefly 

 under the sarcolemma. If liposomes were present in the body of the large fibers at all, 

 they were too small to be distinguished with the 1/12 oil immersion. In many sections 

 of this poor fish the intermediate-sized fibers had their liposomes chiefly at the surface, 

 whereas the central portion of the fiber was comparatively free of liposomes. Disappear- 

 ance of fat is not accompanied by any signs of degeneration at this stage. The struc- 

 tural detail is clearer and very sharp and distinct, as shown in figure 13, plate viii. 



In teased preparations where one has a view of a fiber for some considerable length 

 it appears that the Warrendale pink muscle is relatively rich in liposomic fat. In the 

 best salmon there is even a greater amount of intracellular fat in the pink muscle than 

 at the Ilwaco station. The chains of liposomes are more continuous and the size of the 

 individual liposomes relatively greater. In the small fibers particularly this comparison 

 holds. In fact, it often happens that in the smallest fibers the liposomes have reached 

 a size at which adjacent ones coalesce, a phenomenon the significance of which is dis- 

 cussed in another connection. 



While the above comparison is true and striking it is also true that at this station 

 the range of variation in the amount of liposomic fat in the pink muscle is far greater 

 than at Ilwaco. The fattest muscles have a greater amount of intracellular fat, the 

 poorer muscles have a much smaller amount of intracellular fat. 



Caudal pink muscle. — The caudal pink muscle of salmon from the Warrendale 

 station shows the sharpest contrast as regards the amount and arrangement of the fat. 

 In salmon no. 120 the intermuscular fat is all gone except along the connective 

 tissue septa where it is present in scattered but medium-sized drops. In the poorer 

 salmon the amount of intermuscular fat in the caudal pink is practically nil. Here and 

 there in the thicker septa between bundles of fibers one will find an individual droplet 

 or a group of three or four droplets not more than 4 or 5 /( in diameter. 



The intramuscular fat of the caudal pink muscle is very slight indeed even in the 

 fattest fish. The smallest fibers are fairly well supplied with liposomes which run in 

 chains comparatively evenly distributed throughout the sarcoplasm. In these instances, 

 however, there are distinct groups of liposomes under the sarcolemma, but at the surface 

 of the sarcoplasm. There is a distinct difference in size between the surface liposomes 

 and the deep ones. The former range from i to 1.5 /i in diameter, while the latter are 

 only from 0.2 to 0.4 /x in diameter in fish no. 120. In salmon no. 126 the liposomes are 

 still present in the small fibers, having much the same arrangement as that just described 

 and averaging about 0.4 // in diameter. 



In the intermediate and in the larger sized fibers the amount of intracellular fat is 

 very small. In the larger fibers only an occasional group of very tiny liposomes at the 

 surface of the fiber can be seen. In the intermediate fibers there are now and then 

 fibers which have a comparatively even sprinkling of tiniest liposomes throughout the 

 mass of the protoplasm with somewhat larger liposomes at the surface of the fibers. On 



