126 BULLETIN OF THE BUREAU OF FISHERIES. 



It is to be assumed that the muscle fibers absorb the fatty bodies from the lymph 

 and blood, presumably as soluble fatty acids and glycerin. The fatty bodies of the 

 blood and lymph are derived from the stored fat by a process of lipolysis. To that 

 extent to which the store of intermuscular fat of the pink muscle is eroded by this 

 process of lipolysis will the percentage concentration of the cleavage products of the 

 pink muscle lymph be high. From the lymph the fat cleavage products dialyse directly 

 into the pink fibers and become available for oxidation. In the early stages of the fast 

 there are numerous tissues besides the muscle containing an excess of stored fat; the 

 digestive tube, the pancreas, the liver, the skin, etc., as well as the connective tissue and 

 the muscles. Loevenhart ° has stated that the limits of lipogenesis are "nearly propor- 

 tional to the amount of enzyme acting" and "nearly independent of an excess of ethyl 

 butyrate" in the experiments of his series. Hence, with increasing production of lipase 

 in the blood there is an ever-increasing percentage of fatty bodies thrown into solution 

 in the blood and lymph. 



Hand in hand with the increase of fatty bodies in the blood and lymph will go an 

 increase in fatty products in the substance of the muscle fibers. Muscular oxidations are 

 not rapid enough to keep down the increasing quantity of fatty bodies, hence they will 

 diffuse through the muscle protoplasm in considerable excess. The lipase of the blood 

 and Ivmph will also diffuse into and be present in the muscle fiber, a fact demonstrated 

 for other muscle tissues. Under the law of reversible lipase action this excess of fatty 

 cleavage bodies is bound to be reconverted into and deposited as neutral fat. Thus arise 

 the chains of microscopic liposomes of the pink muscle at the beginning of the salmon 

 fast. 



The number and size of the chains and of the individual liposomes in the pink 

 muscle, therefore, is a result of the interaction of a number of factors, chief of which are 

 the following : 



a. The relative abundance of the stored fat in the tissues of whatever source, i. e., 

 the gross amount of fat available for lipolytic erosion in all parts of the body. 



b. The relative abundance of lipase throughout the body, chiefly of the blood and 

 lymph, but having origin in lipase producing tissues. 



c. The structural and physical factors controlling the rapidity of the absorption 

 from the blood and Ivmph into the muscle fibers; i. e., the sarcolemma, sarcoplasm, etc. 



d. Especially the rapidity with which the fatty bodies are utilized, oxidized, by the 

 muscle sarcoplasm. 



The constants of lipase action have not yet been determined sufficiently to enable 

 one to apply to this specific instance definite governing laws. It is hoped that some- 

 thing may be accomplished along this line as this work progresses. At present, however, 

 one may say that in a general way e, the size and number of the liposomes in any given 

 fish's pink muscle, will vary directly as a, the abundance of stored fat, b, the relative 

 abundance of lipase, c, the structural and physical factors governing the diffusion of the 

 lipolysed products, and inversely as d, the rate of oxidation of fats in the muscle fibers. 

 The relation may be expressed as follows: 



a 

 where k \s a. complex constant representing the unknown facts and relations referred 

 to above. 



' '\ IvOvenhart, op. cit.. p. 350. 



