[Pboc. Roy. Soc. Victoria, 24 (N.S.), Pt. II., 1911]. 



Aht. XVIII. — Osmotic Eqiiilihration in the Living Body. 



By JUDAH LEON JONA, D.Sc, M.B., B.S. 

 (Assistant -Lecturer in Physiology in the University of iVlelbourne). 



(Communicated by the Honorary Secretary). 



[Eead 12th October, 19111 



The primitive form of life from which all present existent 

 forms of animal life are derived was, according to the Dar- 

 winian theory, a unicellular organism, analogous to the Amoeba, 

 which, undoubtedly, lived in the ocean. From this form were 

 evolved the simple coelenterates, and ultimately animals 

 appeared which contained in their organisation a closed cavity 

 which contained a fluid undoubtedly derived from the environ- 

 ment, the ocean. This closed cavity and its contained fluid 

 •were ultimately destined to become the circulatory system and 

 the circulating fluid (blood) of the higher animals. 



When these primitive animals left the sea and took to an 

 estuarine life as a preliminary to living in the mud and, ulti- 

 mately, on dry land, they took with them, contained in this 

 body cavity, a fluid which had the same chemical composition 

 as the ocean, their original home. 



In the future evolution of this type of terrestrial animal, it is 

 legitimate to postulate that the composition of this fluid re- 

 mained about the same, and thus the animal, its cells attuned to 

 a fluid of this composition, and by its terrestrial life removed 

 from any chance of being exposed to any alterations in the 

 composition or concentration of this circulating fluid, was 

 given every opportunity of ascending in the scale of evolution. 



We have here the first example of standardisation in the 

 body, one. of the principal stepping-stones to the proper and 

 efficient evolution of the individual and race, a process well 

 exemplified in the high degree of standardisation met with in 

 the higher mammals, not only of the osmotic pressure of the 



