66 Physiology of the Kidney 



brain are integrated into images of consciousness and brought 

 into an unstable focus to form that fleeting entity which we 

 call personality, or Self. But let the composition of our in- 

 ternal environment suffer the slightest change, let our kid- 

 neys fail for even a short time to fulfill their task, and our 

 mental integrity, our personality, is destroyed. 



There are those who say that the human kidney was cre- 

 ated to keep the blood pure, or more precisely, to keep our 

 internal environment in an ideal balanced state. I would 

 deny this. I grant that the human kidney is a marvelous 

 organ, but I cannot grant that it was purposefully designed 

 to excrete urine, nor even to regulate the composition of the 

 blood, nor to subserve the physiological welfare of Homo 

 sapiens in any sense. Rather I contend that the human kidney 

 manufactures the kind of urine that it does, and it maintains 

 the blood in the composition which that fluid has, because this 

 kidney has a certain functional architecture: and it owes that 

 architecture not to design or foresight or any plan, but to 

 the fact that the earth is an unstable sphere with a fragile 

 crust, to the geologic revolutions that for 600 million years 

 have raised and lowered continents and seas, to the predacious 

 enemies, and heat and cold, and storms and droughts, the un- 

 ending succession of vicissitudes that have driven the mutant 

 vertebrates from sea into fresh water, into dessicated swamps, 

 out upon the dry land, from one habitation to another, per- 

 petually in search of the free and independent life, perpetu- 

 ally failing for one reason or another to find it. 



It is more than an antiquarian impulse that leads me to 

 close this lecture by two quotations. About the 5 th century, 

 a Persian philosopher who is well known to all of you re- 

 marked : 



