FISH-LIVER OILS 



499 



easily removed by a simple method of extraction; in others the oil is removed 

 from the hvers only after breaking up the molecule of protein composing the 

 liver. In the latter case a more complicated method of extraction is required. 



The viscera, including the stomachs and gonads of some species of fish, contain 

 appreciable amounts of vitamin A; these are not ordinarily included when the 



INCHES 



(.Courtesy U. S. Fish and Wildlife Service) 



Fig. 23-1. Ventral view of fish livers; top, rockfish; middle, 

 lingcod; bottom, halibut. 



livers are purchased unless specifically indicated by the buyer. Processing viscera, 

 including the livers, is confined almost entirely to halibut and sablefish. The 

 livers of other species are usually purchased free of viscera. The processes which 

 have been developed for the extraction of vitamin A oils from livers are generally 

 not applicable to viscera, and for this reason it is not generally considered economi- 

 cal to handle both in the same plant. 



The center of production of vitamin A-bearing oils is on the Pacific Coast of 

 the United States. The hvers of the fish found in that area have a higher vitamin 

 A content than those in any other coastal area of the United States. This has 

 never been explained satisfactorily, but even similar species of fish livers vary to 



