474 MICRO-OKGANISMS IN WATER 



BACILLUS MEMBRANACEUS AMETHYSTINUS 



LIQUEFIES GELATINE 



Authority. — Eisenberg, Bahteriologische Diagnosiik, 1891, p. 421. 



"Where Found.— In well-water of Spalato (Jolles). 



Microscopic Appearance. — Short bacilli with rounded ends, on the average 

 from 1*0 to 1*4 fi long and 0*5 to 0*8 fi broad. They are irregularly aggregated to- 

 gether, arwi some individual bacilli stain more strongly at the ends than in the. 

 middle. They are not motile. Spore formation uncertain. 



Cultures. — 



Gelatine Plates. — In two to three days on a thickly sown plate small homo- 

 geneous dark violet centres make their appearance, which in the course of the 

 next few days become surrounded by a zone of liquid gelatine. In from one to tw* 

 weeks the whole of the gelatine is fluid, andthe colonies which have hardly increased 

 in size float in the clear liquid. When fewer colonies are present on the plate they 

 give rise in three to four days to yellowish white expansions with a jagged edge, 

 resembling the typhoid colonies ; the gelatine in the vicinity of the expansion only 

 becomes softened after from ten to fourteen days. The colony meanwhile has- 

 become deep violet in colour, and after from three to four weeks it floats as a large 

 violet pellicle on the slightly liquid gelatine,, resembling a membrane stained, 

 with gentian violet. 



Gelatine Tubes. — Forms a superficial yellowish white expansion with a 

 jagged edge, which after ten to fourteen days, or even longer, becomes violet in 

 colour,which starts from the centre. Liquefaction only gradually commences. After 

 about four weeks a thick dark violet pellicle covers the sunken and softened 

 gelatine, whilst the whole contents of the tube do not become fluid until after 

 from two to three months. 



Agar-agah. — Exhibits after twenty-four hours a thick yellowish white milky 

 expansion, which only assumes a violet colour after eight to ten days have elapsed. 

 In three to four weeks it has grown into a very wrinkled expansion of a magnifi- 

 cent deep violet colour, having a metallic lustre. The agar beneath remains, 

 uncoloured, and the growth is easily removed from its surface. 



Potatoes.— Grows very slowly, forming a dirty yellow to oHve-green coloured 

 expansion. 



Broth. — Grows very slowly ; after some weeks a violet deposit is formed, and 

 a violet pellicle is produced on the surface of the dark brown-coloured liquid. 



Remarks. — It grows only at 15° to 20° C. ; no growth takes place at 37'5°. 



BACILLUS CAEEULEUS 



LIQUEFIES GELATINE 



Authority. — Smith, *A new Chromogenic Bacillus,^ Medical News, 1887^ 

 vol. ii.. No. 27, p. 758. 



"Where Found. — In water from the river Schuylkill. 



Microscopic Appearance.— A bacillus 2 to 2-6 /i long and -5 ^ broad ; fre- 

 quently forms leptothrix-iike threads. 



Cultures.— 



Gelatine Plates. — Forms cup-like liquid depressions. No colour is visible- 

 in the depth of the gelatine, but the surface colonies exhibit a faint blue 

 tint. 



Potatoes. — Grows at the ordinary temperature, producing a beautiful dark 

 blue growth, which later becomes an intense blue black. It only grows on the 

 surface of the potato. 



Bemarks. — The pigment is contained in the cells, and is not extracted by water^ 

 alcohol, or acids. The bacillus is not pathogenic. 



