THE PHYSIOLOGY OF EXCRETION. 107 



crystallize in regular systems. We do not know why; yet we 

 must abstain from introducing teleological factors into the sci- 

 ence of life, because science has to work with given and com- 

 prehensible factors, and has to conform to the nature of our 

 own intellect, which is unable to form any adequate teleological 

 conception. If we try to soar above the limits which nature 

 has put to the faculties of our brain, we might as well give up 

 research, cross our arms, and say Credo, or else yearn for 

 Nirvana. 



