COMPOSITION OF FISH 347 



amine and phosphatidyl serine, 5 per cent sphingomyelin, 1 per cent 

 phosphoinositides, and lesser amounts of sterols, cerebrosides, and un- 

 identified components. Large proportions (nearly half) of the fatty acids 

 in these phospholipids consisted of the very highly polyunsaturated 

 C20 — 5 double bonded and C22 — 6 double bonded fatty acids. 



Fish liver oils sometimes contain relatively high proportions of non- 

 triglyceride components which make up the unsaponifiable portion of 

 these oils. For example, many shark-like fishes contain alkoxydiglycerides. 

 In the common dogfish such compounds occur in amounts up to 15 per 

 cent and in the ratfish to an even higher proportion. These alkoxydiglycer- 

 ides consist of a glyceryl ether at the ether linkage, principally selachyl 



* Values are much higher( about 200 mg %) 

 for calcium in canned fish if the bone is in- 

 cluded. 



alcohol, batyl alcohol, or chimyl alcohol. Not only are these glyceryl 

 ether components less unsaturated than are the fatty acids of most fish 

 oils but also the fatty acids esterified to the diglycerides portion are less 

 unsaturated, containing considerable proportions of monoenes^ 



Some shark liver oils also contain very considerable quantities of some 

 hydrocarbons, particularly squalene (an unsaturated C30 hydrocarbon 

 with 6 double bonds). Basking shark liver oil contains nearly 50 per cent 

 squalene. 



Inorganic Components. Fish probably contain, at least in very small 

 amounts, practically all of the elements occurring in sea water. Table 

 26.9 lists those occurring to the greatest extent. In addition, trace, yet 



