474 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tbo action of light. Tho purple bactoria in fact givo off oxygen under 

 the influence of light, and culture-experiments showed that tho develop- 

 ment, growth, and multiplication of purplo Schizomycctcs is only per- 

 manently possible in the light. 



The elimination of oxygen is intimately associated with tho presence 

 of bacterio-purpurin in the living protoplasm. Yet, as with chlorophyll, 

 it stands in no simple relation to the saturation of tho plasma witii tho 

 pigment. In individual cases, however, it is proportionate for different 

 wave-lengths to the absorbed energy of the light. Ultra-red (gas or sun- 

 light deprived of visible rays by means of iodine in sulphido of carbon or 

 pure ultra-red between 0'80 and 0*90 /x wave-lengths) acts less weakly 

 than perfectly mixed light. The visible red, tho extreme ultra-red, 

 violet, and ultra-violet, gave, at least in the spectrum of powerful gas- 

 light, no obvious effect. 



Bacterio-purpurin is therefore a true chromophyll ; apparently 

 not a simple chemical body, but a mixture like other chromophylls 

 (chlorophyll, diatomin, rhodophyll) ; and is distinguished from tho 

 latter most strikingly by the absence of the green constituent. It 

 demonstrates anew that the elimination of oxygen can be effected in tho 

 light by non-green pigments and by every kind of wave-length, and that 

 in all cases, for the different wave-lengths it is proportional to tho 

 absorbed energy of the light. 



-^-*«5=**-*- 



