76G TRANSACTIONS OP SECTION 1. 



T28 per cent, in the cod and pollock, while in the mammal the total salts are La 

 the neighbourhood of 0'90 per cent. 



Analyses of the blood in the king crab (Limulus 'polypliemus) and of the lobster 

 (Homaras Americanus) gave in total salts 2'982 and 2852 per cent, respectively, 

 which are approximately the concentrations of the sea waters of their habitat. 

 The ratios of the elements as found were : — ■ 



The remarkable agreement between the ratios in Limulus and Avrdia, and again 

 between these and those of sea water, shows that the composition of the ocean 

 determines the inorganic composition of the blood in Limvlus, which with its 

 ancestral forms has been oceanic since the beginning of the Cambrian. The only 

 important differences in these ratios is to be found in the SO, in both forms, being 

 not more than two-thirds of that in sea water. 



In the lobster the ratios for the magnesium and the 80 3 are far behind those 

 found in Limvlus. The reason is that the resistance which the absorbing mem- 

 branes in the lobster exercise towards the magnesium and the S0 3 has not been 

 so much weakened as in Limulus. 



The difference not only in the ratios of the elements but also in the concentra- 

 tions of the total salts between Limulus and the dogfish, both of which, as pointed 

 out, have always been oceanic, and between the lobster on the one hand and, 

 on the other, the cod and pollock, all three of which have been oceanic since the 

 Cretaceous, is to be referred to the character of the vertebrate kidney. The 

 uniformity in inorganic composition of the blood plasma throughout vertebrates 

 is due to the specific action of the vertebrate kidney, the primary and only function 

 of which in eovertebrates was, apparently, to keep the inorganic composition of 

 the blood uniform in all habitats. This and other facts make it necessary to 

 regard the kidney as the most ancient and typical vertebrate organ, and to con- 

 clude that it acquired its characteristic function when the ocean had a saline 

 concentration about one-third of that of the ocean of to-day, and when also the 

 oceanic ratios were approximately those now found in vertebrate blood plasma. 



The inorganic composition of the blood plasma may, consequently, be regarded 

 as pakeo-oceanic in character, an heirloom of life in the sea of remote geological 

 time. 



2. The Inorganic Composition 0} the Blood Plasma in ihe Frog after a long 

 period of Inanition. By Professor A. B. Macallum, F.R.S. 



The blood plasma of the laboratory frog in spring gives a A ranging from 

 -0-38° to -0-40° C. The salts in amount vary from 0'57 to 0-64 per cent., and 

 they account for practically the whole of the a' (-0-395° out of -0-40° C). In 

 consequence of this low concentration of the salts the blood as it is collected 

 lakes spontaneously and more or less freely. This is probably the reason for the 

 variations in volume of the red corpuscles in the blood in different frogs as 

 observed, for the maximum volume as found with the hiematccrite was 29 per 

 cent, and the minimum 13 per cent. 



The ratios of the potassium, calcium, and magnesium were approximately 

 those found in mammals, except in the low value of the magnesium and in the 

 potassium, the excess of which was due to laking. 



Na K Ca Mg 



100 .. .. 127 .. .. 3-98 .. .. 0-395 



The red corpuscles are rich in potassium, amounting to about 0-200 per cent. 

 and apparently free from sodium salts. The sodium in the plasma ranges from 

 0-1874 to 0-1975 per cent., while the chlorine in two determinations from different 

 eamnles gave 0-252 and 0-267 per cent. 



The lowest A found by Dekhuyzen in the blood in the normal frog was 

 -0-464°. The highest A determined by him in any other vertebrate Was found 

 by Dekhuyzen in Tinea vulgaris (-0-466°). 



