178 CHAS. W. GREENE 



of the droplets and among these larger drops, sometimes in close 

 approximation to them, will be found numerous smaller droplets. 

 The smallest droplets present are visible only under the oil im- 

 mersion lens. In numerous instances the smallest droplets are 

 found between the adjacent fibrillae. 



In the normal tissue great quantities of fat are also found over 

 the surface of the fiber but under the sarcolemma. That is to 

 say, the fat is stored between the sarcolemma and the muscle 

 substance. There is great variation shown by the individual 

 fibers. Some of them present almost continuous rings of fat 

 droplets, especially in the younger fish, while others show fat 

 around only a small portion of the surface. In the scarlet red 

 stained material it is not always easy to demonstrate this relation- 

 ship of the fat droplets, but in paraffin material stained by Mal- 

 lory's aniline blue stain it is easy to confirm the fact that the fat 

 is within the sarcolemma. 



The appearance of the fat and its relations within the dark 

 muscle fibers, especially within the sarcoplasm of the fibers, is 

 best shown by the two figures, one of which (fig. 1) gives the posi- 

 tive picture obtained by scarlet red staining of frozen sect'ons of 

 formalin-fixed tissue; the other (fig. 2) the negative obtained by 

 the imbedding method. The presence of fat within muscle fibers 

 is well enough known, but I have thus far found no reference in 

 the literature to any such concentrated loading as is represented in 

 this dark muscle from the king salmon. My general report on 

 this work, together with comparisons with other muscular tissues 

 in the king salmon will give evidence for making the assumption 

 expressed in the title, namely, that we are dealing here with a new 

 and special type of fat-storing muscle. 



The functional significance of this type of muscle seems to me 

 to be found largely in the fact of its ability to store and to liber- 

 ate again such unusual quantities of fat. The muscle has the 

 function of lipogenesis strongly developed. It would seem that 

 it is illustrative of one specific tissue in which Loevenhart's sug- 

 gestion of a lipogenesis is a specific physiological function. To 

 what extent this function supersedes or displaces the general 

 contractile power, if it does either, remains to be determined. 



