1902-3.] The Pal^ochemistry of the Ocean. 539 



II.— The Origin of the Physiological Relation of the 

 Chemical Element in Blood Plasma. 



I have thus dealt at some length upon the importance of the 

 history of sea water, and with Joly's views and those of his critics, 

 because all this leads up to a question which is of very great importance 

 to the physiologist. The life of the globe in the earlier geological ages, 

 so far as the strata reveal to us the past history of the earth, as already 

 pointed out, was closely associated with the sea. It is indeed almost 

 universally assumed that life began in the ocean and continued in 

 association with it alone till the close of the Cambrian period, although 

 the presence of graphite in Cambrian and older rocks seems to indicate 

 that vegetable organisms were accommodating themselves to a land life. 

 Even this may not be an exception, for these rocks must have been laid 

 down under water, and therefore their organic remains would be those 

 of the sea. If accordingly we could know what the composition of the 

 sea water in the Cambrian and pre-Cambrian periods was, we would, in 

 all probability, be able to determine some of the chemical and physical 

 forces to which living matter was then subjected and thus explain the 

 relations which obtain to-day in living matter between it and its 

 salts. In a recent paper* I have pointed out that the relative propor- 

 tions of the elements, sodium, potassium, and calcium in the plasma of 

 the blood are surprisingly very like those which are found in the ocean 

 water of to-day, and that the differences which obtain between the two 

 series of proportions of these elements, may be explained on the ground 

 that such proportions in the blood plasma are those that obtained in 

 ancient sea water when the ancestral form of Vertebrates, in which sea 

 water was the circulatory fluid, as it is in many marine forms to-day, 

 acquired a closed circulatory system. That the ancient proportions are 

 reproduced to-day in all forms, which have a closed circulation, I 

 attribute to the influence of heredity, the cells of the organisms having 

 for ages been associated with the sodium, potassium, and calcium in 

 certain proportions, and having been accommodated to them, the 

 relations ultimately became so fixed that living matter reproduces the 

 ancient proportions in the fluids which bathe itself There is one point 

 in which the proportions in the circulatory fluid and those in sea water 

 differ, and that is in respect to the magnesium. In the sea water of to- 

 day there are 11.99 parts of magnesium for every 100 of sodium, while 

 in plasma there are 0.8 parts of magnesium to 100 of sodium. This is 



* On the Inorganic Composition ot the Medusae, Aureh'a flavidula and Cyanea Arctica. Journ. of 

 Physiol., Vol. 29, p. 213, 1903. 



