BIOLUMINESCENCE IN BACTERIA 377 



left) which gave out a soft and perfectly steady blue-green light 

 that was strong for about 14 days and weaker thereafter. With 

 these lamps he was able to tell the time by his watch, observe the 

 scale of a thermometer, read large print on the pages of books, 

 recognise the face of a person 1-2 metres distant, and make photo- 

 graphs of statuettes (Fig. 167, right), thermometers, and other 



Fig. 1(56. — A pliotograpli of some luminescent colonies 

 of Bacferium jyhosphoremn, made with their own light. 

 The colonies, days old, are growing in nutrient 

 gelatine in a Petri dish covered with a glass plate. 

 Time of exposure, 15 hours. Photographed by Hans 

 Molisch. From his Leuchtende Pflanzen, Taf . I, Fig. 2. 



objects. Molisch has suggested that bacterial lamps, on account of 

 their cheapness, long unbroken luminosity, lack of smell, and 

 absence of danger, might find some use — like certain luminous 

 beetles in tropical lands — as night-lights.^ 



To obtain luminous bacteria on meat Molisch ^ advises that one 

 should proceed as follows. Procure on successive days a few small 

 pieces of meat (beef, veal) from a butcher's shop. Put them in 

 a crystallising dish and pour over them a little 3 per cent, sodium 



1 Hans Molisch, Leuchtende Pflanzen, Jena, 1904, p. 124. - Ibid., pp. 57-58. 



