NUTRITIVE' VALUE OF FISH AND SHELLFISH 



541 



of eggs of birds. They regard this constant occurrence of manganese 

 in animals as evidence of a physiological significance. Future re- 

 search may be expected to bring forth other results dealing with what 

 have been regarded as unimportant or insignificant substances in 

 the animal organism, perhaps havmg a bearing on the problems of 

 health under conditions of civilization. 



Meanwhile there is some satisfaction to be found in the fact that 

 fish as a class contain the elements necessary for life, whether or 

 not we know at the present time which ones are necessary or impor- 

 tant or in what way. If we subsist on foods derived from the land, 

 deficiencies may and do occur; they seem much less likely in fish, 

 especially those from the sea. 



CONSTITUENTS OF SEA WATER 



The following are the more important elements present in solution 

 in sea water (Clarke, 1920) : 



Element or radical Per cent 



Chlorine 1. 935 



Bromine . 0066 



Sulphate (SO4) .269 



Carbonate (CO3) . 0072 



Element or radical Per cent 



Sodium 1.0171 



Potassium . 0387 



Calcium .0419 



Magnesium . 1304 



Besides these, the following elements exist in smaller quantities. 

 Figures, where given, are milligrams per liter of water: 



Iodine 2.38. Found in considerable quantities in ashes of seaweeds. 



Fluorine 0.S22. Found in the shells of moUusks. 



Phosphorus Present as phosphate. 



Arsenic 0.01 to 0.08. 



Silicon 0.2 to 1.4. 



Boron Present in sea water and in ashes of marine plants. 



Lithium Present in sea water. 



Rubidium 14. 



CsBsiuni Present in sea water. 



Barium Can be detected by ordinary methods. Pre.seut in ashes 



of seaweeds and marine boiler scale. 

 Strontium Ca.n be detected by ordinary methods. Present in ashes of 



seaweeds and marine boiler scale. 



Aluminum Easily detected by direct methods. 



Iron Basil:/ detected by direct methods. 



Manganese Easily detected. Abundant in mud of ocean bottom; 



present in ashes of seaweeds, and in shells and tissues of 



moUusks. 



Nickel Present in ashes of certain marine plants. 



Cobalt Present in ashes of certain marine plants. 



Copper Present in sea water and in ashes of some seaweeds and 



corals. 



Zinc 0.002. 



Lead Present in certain corals and conchs. 



Silver 0.01 toO. 169. 



Gold 0.005 to 0.016. Also present in kelp and bottom dredgings. 



Radium 0.000000000017. 



ASSIMILATION AND CONCENTRATION OF MINERAL SUBSTANCES 

 BY MARINE PLANTS AND ANIMALS 



Some of the elements are present in sea water in merest traces, 

 yet plants and animals living in the sea have the ability to extract 

 them as needed and concentrate them. For example, iodine exists 

 in sea water to the extent of about 2.38 milligrams per liter, yet 



