540 U. S. BUREA.U OF FISHERIES 



are only relatively so; it is the view of chemists that all substances 

 aro soluble in some degree, however slight, in water. 



In view of these facts, the reader need not be surprised to find in 

 the ocean very many if not all the elements known to exist on the 

 earth — eighty-odd in number. Thirty-two of them have been 

 definitely detected by chemical methods, and most of the 32 have 

 been quantitatively determined. The animals and plants that live 

 in the sea live all their lives in a medium that contains every chemical 

 element that can be needed, and the food on which each animal 

 lives has also grown in this universal solution. It is difficult to 

 imagine a lack in their environment of any substance useful or 

 necessary to life. 



This can not be said of land animals and plants that derive their 

 mineral constituents from the soil. The science of soil fertility and 

 fertilizers is based on widespread deficiency of important substances 

 in the soil, such as nitrogen, phosphorus, potassium, calcium, and 

 magnesimn. In man and other land animals disorders and diseases 

 are known to be caused or influenced by deficiencies of calcium, 

 phosphorus, iodine, iron, etc., and research continues to bring out 

 facts of tliis kind. It has been shown that even the minutest traces 

 of certain mineral substances may have a profound effect on life 

 processes. 



For example, it was discovered several years ago (Bayliss, 1924) 

 that zinc in infinitesimal quantity has an extraordinary effect in 

 stimulating the growth of the mold fungus Aspergillus, one part of 

 zinc in 25,000,000 parts of water increasing growth 50 per cent. 

 It was revealed by further research that manganese in extreme 

 dilution had a similar effect; and that zinc and manganese had a 

 stronger effect than either alone. In the presence of zinc and iron 

 in traces the fungus grew freely but bore its fruit (conidia) only 

 if traces of manganese were present. These metals, though requu-ed 

 in only infinitesimal quantities, are considered absolutely indispen- 

 sable to the normal functional capacity of protoplasm. 



Copper has a similar but opposite effect, being destructive to 

 alg5i3 and other lower plants. A copper coin allowed to remain in a 

 liter of distilled water four days gave up only 1 part of copper to 

 77,000,000 parts of the water, jet the water killed the alga Spirog^Ta 

 in one minute. It may or may not be significant that copper is 

 found habitually, zinc often, and manganese occasionally in human 

 bile (Hammarston and Hedin, 1915), and that the human intestine 

 is the normal habitat of a diversity of fungi to which these metals 

 may bear an important relation. 



Manganese has been found to occur in fairly constant quantity 

 in the blood and various organs of man and seems to be a normal 

 constituent (Rciman and Minot, 1920). The results of anal}^sis 

 of four adult brains and one fetal brain indicate that copper and zinc 

 are normal constituents of the human brain (Bodansky, 1921). 

 From analysis of one fetal brain it appears that during intrauterine 

 life there is a more rapid storage of zinc and copper in tlie brain than 

 there is after birth. In this respect the behavior of these elements 

 is similar to that of iodine and other inorganic constituents. Other 

 investigators (Bertrand and Medigreceanu, 1912) found, by 250 

 determmations on about 60 different species of animals, the con- 

 stant presence of manganese in all of them excepting only the white 



