SALT AND WATER IN LIFE AND GROWTH 105 



2. OUR BLOOD AS THE DESCENDANT OF THE ANCIENT OCEAN 



Following this train of thought, we are led to assume that 

 the internal circulating fluid — the blood of higher animals- 

 was developed from the water of the ocean. Is there evi- 

 dence to corroborate this view? 



The following experiments are helpful because they 

 demonstrate the indispensibility of all the various salts the 

 ocean contains. As an object of experimentation, we select 

 one of the more highly developed fishes, a so-called bony 

 fish, Fundulus Heteroclitus. This fish has a dense skin 

 which completely shuts off all the interior tissues of its 

 body from the surrounding water. It has gills for res- 

 piration, a beating heart, a circulating blood, and organs 

 for digestion and excretion. It can live either in the ocean 

 or in a river, and frequently changes from one to the other. 

 In the laboratory, this fish can even be placed in distilled 

 (chemically pure) water, without suffering damage. 



Very surprising things occur if we place this fish in an 

 artificially prepared solution of pure salts. The ocean 

 water contains several different kinds of salts. Among 

 them is ordinary table-salt (sodium-chloride), which makes 

 up approximately 3.5% of the sea water; the other salts 

 are present only in negligible quantities: about 0.2% each. 

 These minor constituents are the so-called lime salts, and 

 potassium and magnesium salts. One might suppose that 

 a fish which can live in ocean water or in distilled water 

 should also be able to live in a simple table-salt solution. 

 This, however, is not the case at all; all fish die very quickly 

 in such a solution, particularly if the salt content about 

 equals that of the ocean. These striking observations were 

 first made by Jacques Loeb (1859-1924), biologist of the 

 Rockefeller Institute, who indefatigably investigated the 

 cause of this strange phenomenon and greatly helped to 

 clarify it. 



