406 PROTOPLASM 



not sufficient for normal growth. Fimke finds that in blue light, 

 plants do as well as in normal light ; while in red light alone, they 

 become etiolated. 



Polarized Light. — Organisms are accustomed to direct light. 

 Only comparatively rarely are they subjected to reflected light. 

 Reflected light is polarized. It has recently been found that 

 polarized light has a marked effect on living and nonliving matter. 

 This form of light consists of unilateral vibrations swinging 

 parallel to each other in the same plane. Ordinary light vibrates 

 in all planes; it is propagated from its source in all directions. 

 The light from the moon is polarized because it is reflected. Our 

 eyes cannot distinguish polarized from ordinary light, but living 

 tissues and photochemical reactions apparently possess the 

 capacity to distinguish between them. The work of David 

 Macht and of Bhatnagar indicates that polarized light accelerates 

 chemical reactions (between amalgams of the alkali metals) ; 

 profoundly affects the properties of drugs; and stimulates the 

 growth of bacteria, yeast, and seedlings. It seems that the 

 first experiments of this nature, on the conversion of starch by 

 polarized light, had been done earlier in England. That we 

 shall yet have to grant the possibility of there being some truth 

 in the old superstitions that moonlight is harmful — from which 

 are derived such familiar expressions as ''lunatic," "moon blind," 

 and mondsuchtig — and that certain fruits are ripened primarily 

 by the light of the moon seems unlikely, if for no other reason 

 than that the light of the moon is very feeble; to have any effect, 

 it would have to exert its influence over a long period of time. 



Infrared.— At the long-wave end of the visible spectrum are 

 the infrared rays. These have at last come into their own, the 

 stage until now having been held by ultraviolet. Infrared rays 

 play a very significant part in life — more so than we have hereto- 

 fore realized. They are coming to the fore in physicotherapy 

 for the treatment ("baking") of strained muscles. In photog- 

 raphy, also, infrared rays give pictures of greater depth and 

 clarity on plates sensitive to them. Reference has already been 

 made to the infrared as a source of energy for plants. 



Ultraviolet. — Just beyond the short-wave end of the visible 

 spectrum lie the ultraviolet rays. These have come to play so 

 important a part in our daily lives that nearly everyone now 

 knows of their necessity to our well-being. Perhaps the most 



