CHAPTER XV. 



PHOTOGENIC BACTERIA. 



99. The Genus Photobaeterium. 



THE first occasion of witnessing the phenomenon known as marine phosphorescence 

 will never be forgotten by the beholder. The boat cleaving the gleaming waves 

 inscribes its track in glittering lines, and every movement of the water causes 

 pronounced phosphorescence. A rain of sparkling drops of light trickles from 

 the poii-ed oar, each apparently becoming the centre of fresh evolutions of light. 

 This phenomenon, the sight of which is calculated to captivate the senses of the 

 coast-dwelier, and lead him to forget all trouble for a time, has a counterpart 

 which filled the mind of earlier races of mankind with terror and lent great 

 support to credulity, viz., the phosphorescence of meat, fungi, arid decaying wood 

 in forests. It is only in our own day that an insight into the cause of this 

 wonder has been gained, the microscope, in this case also, being the instrument 

 used to open the door to knowledge. To devote a few words to this phenomenon 

 would be in any event justifiable, on account of its general scientific interest; 

 and moreover, the matter cannot be avoided iu the present work, since some of 

 the facts established in this connection also deserve a brief consideration, both 

 from a chemical and a technical standpoint. 



The first attempt made to investigate this long-known phenomenon in a 

 scientific manner was that of G. FABRIZIO (I.) in 1592. The treatises subse- 

 quently published thereon (up to 1887) are to be found included in a historical 

 and critical review of the subject written by F. LUDWIG (I.). This has been 

 supplemented (up to 1891) by a work issued by O. KATZ (I.) which may be 

 referred to in this place. 



We are indebted to Pfliiger for the first microscopical examination of this 

 phenomenon. He examined, in 1875, the white mucus covering the surface of 

 fish exhibiting a silvery phosphorescence, and found it composed of globules, 

 frequently united to form chains. When these forms were mixed with water 

 and the mixture passed through a doubled layer of dense filter-paper, the 

 latter became phosphorescent, whilst the filtrate ceased to exhibit this property, 

 thus proving the phosphorescence to be due to the minute organisms themselves. 

 These, which were recognised as bacteria, were in 1878 named Micrococcus 

 phosphoreus by Cohn. Wht reas Pfliiger's studies were con ei ned with the 

 carcases of phosphorescent salt-water fish, the first microscopical examination of 

 the phc sphorescent flesh of cattle slaughtered for food was made by Niiesch, who 

 a'so founrl a fission fungus, which he named Bacteriiim lucens, to be the cause. 

 Ludwig, in 1882, showed that a transference of the mucus ot ph( sphorescent 

 sea-fish on to sound animal flesh rendered the latter phosphorescent in turn. 

 Unawaie at the time that the organism Lad already received two i ames, 

 he bestowed on it the title of Micrococcus Pflugeri. This was the first phos- 

 phorescent bacteria obtained (in 1885) as an undoubtedly pure culture. Three 

 years later B. FISCHER (II.) proved the existence of other species, three of 

 which he himself described, one of thim (from the West Indian seas) being 

 named Bacillus y hosphorescer/s, and the other two (found on Geiman shores) 



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