114 ATLAS OF BACTERIOLOGY. 



phosphorescence. Living bacteria can always be ob- 

 tained from phosphorescent cultures, and a filtered 

 culture free from germs is always devoid of phos- 

 phorescence. But although the organism cannot give 

 light without life, it may live without giving light 

 for example, in an atmosphere of carbonic acid. In 

 like manner the muscles cannot contract without life, 

 but they may be alive without contracting. 



According to Beyerinck (C. B., VIII., pp. 716 and 

 651), who includes all phosphorescent bacteria in one 

 (physiological) genus, photobacterium, they require 

 peptone and oxygen in order to produce light. Four 

 of his six varieties also require, in addition to pep- 

 tone, a supply of carbon which may also contain 

 nitrogen. Small amounts of sugar (dextrose, levu- 

 lose, galactose, maltose), glycerin, and asparagin act 

 in this way. In some varieties a higher percentage 

 of sugar causes cessation of the phosphorescence, 

 after the formation of acids and marked fermentation. 



When the phosphorescence is to be maintained, we 

 would recommend a gelatin nutrient medium, made 

 by cooking fish in sea water, to which one per cent 

 peptone, one per cent glycerin, and one-half per 

 cent asparagin have been added. But even in this 

 medium phosphorescence is soon lost if inocula- 

 tions are infrequent, so that in the majority of labor- 

 atories the phosphorescent bacilli do not emit light. 

 By repeated rapid transfers to a suitable nutrient 

 medium we can often succeed in restoring the photo- 

 genic power. I recommend that two salt herrings be 

 cooked in one litre of water, and ten per cent gelatin 

 added to the filtrate without neutralization. 



