352 BACTERIA. 



the ferment-forming powers of the organism are at once 

 interfered with, although growth and multiplication appear to 

 go on much as usual. The process of light production 

 is evidently somewhat of the nature of an oxidation of the 

 food elements within the protoplasm under certain definite 

 conditions, the most important of these conditions being the 

 presence of oxygen and a temperature ranging between 

 3 and 35 C. The Photo-bacterium phosphorescens grows 

 entirely as a surface colony, and although a ferment action 

 is set up, there is no peptonizing power exerted, the gelatine 

 remaining quite solid. 



In a tube culture the organism grows down below the surface along the 

 track of the needle, but the phosphorescence is developed only on the 

 surface, where the organism can obtain a plentiful supply of oxygen. In the 

 neighbourhood of the colonies, after a time, the gelatine takes on a yellow- 

 ish-brown tinge. On all surface growths, whether on agar, gelatine or 

 potato, the growth increases in thickness rather than in surface area. It 

 grows best at from 15 to 25 C. 



A rather pretty story is related in connection with this 

 power of the organism to develop light. A lady, Madame 

 Salomonsen, the wife of Professor Salomonsen of Copen- 

 hagen, was able to obtain photographs of the light bacillus 

 made on gelatine plates and so cultivated them as to form 

 the letters of a complimentary message to M. Pasteur 

 (" Hommage a M. Pasteur") ; the photographs came out very 

 distinctly, and conveyed in a most delicate and striking 

 manner the message which the lady wished to send. 



Photo-bacterium Fhiggeri is the most phosphorescent of 

 all the light bacilli ; it grows in nutrient gelatine as longer 

 and thinner threads than the preceding form. It differs 

 from it also in that, although it exercises its characteristic 

 light function when supplied with peptone and glucose, 

 maltose cannot take the place of glucose. Both organisms 

 in setting up their fermentation processes bring about the 

 evolution of CO 2 and hydrogen. 



If a number of fresh cod or herring, the surfaces of which have not been 

 allowed to dry, be placed between a couple of plates and kept at a tem- 

 perature of about 15 C. or upwards, there may be made out at the end of 

 about twenty-four hours a number of small phosphorescent points, and at 

 the end of a couple of days the whole of the fishes are covered with a 

 phosphorescent glow ; but as putrefaction sets in this glow is gradually 

 lost. There may be separated from these patches an organism 1.5 



