THE KIDNEY 33 



internal environment in respect to both water and salt, 

 as well as for the excretion of waste products. 



Water was available in excess to the protovertebrate, 

 but the concentration of sodium chloride in this water 

 was probably low and highly variable from river to river, 

 from lake to lake, from rainy season to rainy season; and 

 it is not too venturesome to think that the tenacious 

 conservation of salt is one of the most primitive— if not 

 the most primitive— of functions in the vertebrate kidney. 

 The evolution of an equally tenacious conservation of 

 water posed a problem to which entirely different solu- 

 tions were to be foimd by the lungfishes, elasmobranchs. 

 Amphibia, reptiles and birds (the marine reptiles and 

 birds with unique patents of their own) and the marine 

 teleosts; and yet another by the mammals— until after 

 four hundred million years a small, nocturnal rodent can 

 live in a desert burrow without water and the scientist 

 can write in rhythmic heptads: 



Salt and Water 



In the beginning the abundance of the sea 



Led to profligacy 



The ascent through the brackish maters of the estuary 



To the salt-poor lakes and ponds 



Made immense demands 



Upon the glands 



Salt must be saved, water is free 



In the never-ending struggle for security 



Mans chief est enemy. 



According to the bard of Stratford on the Avon, 



The banks were climbed and life established on dry land 



Making the incredible demand 



Upon another gland 



That water, too, be saved. 



Maurice B. Strauss, November 23, 1951. 



