STORAGE OF FAT IN MUSCULAR TISSUE OF KING SALMON. 1 23 



fibers are loaded with liposomes. Those in the dark fibers are large and stain with 

 considerable intensity. 



After a series of experiments on leopard and bullfrogs he says: " It is apparent that 

 if the frog be fed an excessive amount of fat the fat will be rapidly stored up in the 

 muscle fibers." Similar experiments were performed on rats, which were kept on a 

 low ration until the liposomes were removed, then were fed on a ration of fat meat. 

 Under this diet the rats gained in weight and the muscle "fibers filled with liposomes." 



By these brilliant experiments Bell has conclusively proved that the liposomes in 

 the muscles of vertebrates, frogs, and mammals bear a distinct relation to the state of 

 nutrition. The liposomes decrease in number and quantity under a low state of nutri- 

 tion and they can be increased in size and number when the animals receive a favorable 

 food. These experiments are of peculiar importance to the problem of the present 

 paper, since they prove that the presence of the liposomes in muscle tissue is to a certain 

 extent an index of the nutritive condition of the animal in question. It does not of 

 necessity follow that the liposome content of the tissues of an animal in the fasting 

 condition, as in the case of the salmon, will have the same significance. From my 

 previous work, however, and from numerous field observations, I had arrived at the 

 working hypothesis that this was the case in the salmon, a position strengthened by the 

 conclusions of Prof. Bell, which he kindly communicated to me before his results were 

 published. 



The salmon muscle fat is a filtration fat, not a fatty degeneration. It may be 

 stated here that the studies on the king salmon tend to disprove Miescher's theory that 

 the intracellular fat of the salmon muscle, of whatever type the muscle, is a fatty degen- 

 eration, a "Fettentartung";" and support the observ'ations of Mahalanobis that the 

 process is an "infiltration." In short, the observations made on the king salmon have 

 tended to confirm the view expressed above that the intracellular fat of the king salmon 

 is an expression of the nutritive state of the muscle. It is a loading of fat by a process 

 of infiltration, as will be explained more fully, and is not a degeneration of the muscle 

 substance. 



It seems surprising that the test of degeneration versus infiltration should not have 

 been applied to the material under discussion by Miescher and by Mahalanobis. Any 

 examination of histological sections ought to have shown that there was no appreciable 

 and adequate conversion of cell proteins into fat, and this observation would have 

 settled the matter. Transverse sections of dark muscle taken at a late stage in the 

 migration journey show- great regularity of structure, and this structure is of the normal 

 type. If the muscle protoplasm had undergone fatty degeneration commensurate with 

 the amount of fat found in this tissue at th&time of its greatest load of fat, it is evident 

 that there would be little normal protein left, and that this little would show pathological 

 structure. This pathological condition I have never seen except in the extreme ema- 

 ciated condition found at the time of death. Even then it was found to be extensive in 

 only one tissue, the great masseter muscle, and this muscle contained no fat. 



If argument were still lacking to establish an alibi for the "fatty degeneration" 

 process of laying down fat in the salmon muscle, it ought to be supplied by the fact that 

 the young and actively growing dark muscle fibers of the superficialis lateralis muscle 

 bear a heavy load of intracellular fat. These fibers take on a rich deposit of intracel- 



o Miescher, op. at., p. 207. 



