] Q9 the mouse that never drinks 



You and I may be amazed at this feat witliout being 

 greatly stined by it. But to a man with Dr. Smith's en- 

 thusiasm for the kidney it imphes a feat worthy of tlie 

 highest admiration, and with real fervor he lets himself go 

 with a flat statement: "The kidney of the kangaroo rat can 

 concentrate to the greatest extent of any known animal." 



Feeling that I have, perhaps, not admired Dipo suffi- 

 ciently for this particular talent, I let him stand for a few 

 minutes in the palm of my hand. I see again that he is an 

 unusually attractive Httle beast but that there is nothing 

 in his external appearance to reveal what a physiological 

 marvel he is. Nor does he himself seem to be aware of it. 

 Like any ordinary mouse he seems a very modest little 

 creature. Why should the heart of mortal man, or the kid- 

 ney of mortal mouse, be proud? God, the blind chance 

 which is responsible for all evolution, or, perhaps, some- 

 thing somehow in between, has given him the kidneys he 

 needs to live comfortably in the desert. Whether man and 

 mouse want much or little here below depends on how you 

 look at it. But both sometimes get what they want. 



Some chapters ago we commented on the fact that there 

 are three ways of meeting the water problem — ^by econo- 

 mizing, by storing, and by lying low. Dipo introduces us 

 to the fourth and most radical method: making your own. 

 Certain other animals probably make some, but so far as 

 is known, the kangaroo rat is the only one who can make 

 enough to be entirely independent. 



Making your own is not only the most radical solution; 

 it is also the only one of the fom' which is not adopted to 

 a greater or lesser degree by both plants and animals. In 

 other words, no plant can exist, as Dipo can, wdthout some 

 external source of water. In the damp air of the tropics 



