BACTERIUM PBODIGIOSUM. 275 



ing smooth and the structure coarsely granular. On the 

 contrary, the superficial colonies are transparent, pale 

 rose-red to red, very finely punctated, with borders almost 

 or entirely smooth (21, vi; 22, vn). 



Agar Stab. — Stab : Thread-like, without nodules, white 

 to reddish. After keeping longer, a whitish cloudy zone 

 forms about the stab canal (21, in). Surface growth: Al- 

 ready after forty-eight hours completely covered with a 

 smooth, shining growth, the color of which varies from 

 atypical white to typical purple (21, iv). Often it is 

 whitish-gray, shaded with red. The agar, especially be- 

 neath the surface growth, after a longer time becomes 

 colored a garnet- red. 



Agar Streak. — The growth remains limited to the 

 streak; compare agar stab. The water of condensation 

 presents a reddish cloud with a red sediment (21, n; 

 22, i). 



Bouillon Culture. — Diffuse, marked turbidity, with a 

 more or less red-colored, delicate pellicle upon the surface. 

 The bouillon becomes of a gelatinous or oily consistency. 



Milk Culture. — After twenty-four hours it is firmly 

 coagulated; later the coagulum is dissolved and a yellow- 

 ish color produced. 



Potato Culture. — At first a rosy red, moist, flat growth, 

 limited to the inoculation streak. Later it becomes darker 

 in color, is elevated, with a wavy, smooth border, and after 

 five or six days has attained its dark purple color (21, ix; 

 22, x). Sometimes the surface then exhibits a greenish- 

 golden reflex, similar to dry fuchsin. Also the potato 

 culture develops atypically at times, as does that upon 

 agar, and becomes only whitish-gray, orange, or rose-red, 

 instead of dark red (21, x). 



Chemical Activities. — 



(a) The red pigment (prodigiosin) : Develops best upon 

 agar and potato, is insoluble in water, and only externally 

 in color and golden luster is it like fuchsin ; according to 

 Scheurlen, it is apparently also free from nitrogen besides 

 containing no sulphur nor phosphorus. The pigment is 

 readily soluble in alcohol and ether, is turned orange-yellow 

 by alkalis, and from carmine to violet-red by acids. With 

 zinc and hydrochloric acid the pigment, notwithstanding 



