TEXT-BOOK OF BACTERIOLOGY. 185 



its discoverer, was found by Fischer in West Indian waters, and 

 isolated by means of the usual glass-plate process. It is a rod-cell 

 of medium size and with a lively power of spontaneous motion, and 

 which grows without difficulty on our usual media gelatin, agar, 

 bouillon, etc. The gelatin is speedily liquefied, and for a. considera- 

 ble distance around, the appearance of the colonies on the giass 

 plate and in the needle-point cultures is not characteristic. 



As a genuine inhabitant of the tropics, this bacillus requires a 

 comparatively high temperature; it cannot grow at all below 15 

 C., and its maximum of growth is seen at about 30 C., at which 

 temperature the phosphorescence also appears very strikingly. 

 The best place for observing this phenomenon is, however, the sur- 

 face of boiled fishes. When inoculated with a small quantity of 

 artificial culture, it is covered in a few hours with a fatty-looking 

 bacterial coating, which in the dark emits a beautiful bluish- white 

 light. 



Fischer discovered another bacillus in the harbor of Kiel, which 

 has a certain resemblance to this West Indian phosphorescent ba- 

 cillus, and which he calls the "indigenous glow bacillus." Here we 

 again have a motile bacillus whose cells are generally somewhat 

 shorter than those of the species last described. It thrives on gela- 

 tin and agar. It liquefies the former, but more slowly and to a 

 less extent than does its West Indian relative. The colonies soften 

 the solid food medium very gradually. If they reach the surface, 

 circular, bubble-like hollows appear, which look as if clearly stamped 

 out with a punch, and at the bottom of which the yellowish mass 

 of the culture lies, and at last the appearance of such a plate is 

 similar to the violaceus, only that here the pigment is wanting and 

 the growth is more tardy. 



The slowly-softening test-tube culture, with its narrow funnel of 

 liquefaction in the immediate vicinity of the puncture, and the cul- 

 ture on agar offer nothing peculiar. 



In contrast to the West Indian bacillus, the indigenous one re- 

 quires low temperatures, thriving best below 15 C. ; it even be- 

 longs to those micro-organisms which Fischer found able to grow 

 at a temperature below C. 



Down to this point, too, the cultures display phosphorescence, 

 which, as in the West Indian species, is of a bluish-white color, and 

 is developed best on the surface of boiled fishes. 



The third species has by far the widest distribution of all the 

 phosphorescent bacteria, and is, therefore, quite apt to come under 

 notice in the course of our bacteriological investigations. As the 

 phenomenon of phosphorescence also shows itself very markedly in 



