36 Can Science Explain Life? 



for only on the basis of an inherently twisted 

 structure such as the spirazines possess. 



It is an interesting fact that all proteins which 

 have not been subjected to too severe chemical 

 treatment will rotate the plane of polarization of 

 light to the left. The fact that animal proteins 

 have the same direction of rotation as vegetable 

 proteins might be accounted for on the theory that 

 since animals either feed upon plants directly, or 

 upon other animals which do feed upon plants, it 

 might be expected that the structural materials of 

 plant and animal tissues would exhibit some fea- 

 tures in common. It is not so easy, however, to 

 explain why all plant proteins rotate the plane of 

 polarization to the left, unless we are willing to 

 admit that all the present species of plants have 

 descended, not only from a single ancestral spe- 

 cies, but also from a single spirazine. Such an 

 assumption should not be summarily rejected as 

 unreasonable unless we can find some other way 

 of explaining the uniform optical properties of all 

 proteins. If there would be only a few of them, 

 it might be attributed to coincidence ; but since the 

 number of proteins whose optical properties have 

 been determined runs into hundreds, the possi- 

 bility of it being due to mere coincidence must be 

 ruled out. 



