STAB CULTURES 



165 



and beaded when the loosely placed colonies can be distinguished 

 individually. When the colonies are arranged in such a manner 

 that there is some fancied resemblance to papillary excrescences they 

 are known as papillate. An echinate growth indicates one beset with 

 sharp extensions which radiate from the centre into the culture medium. 

 A villous growth shows some resemblance in its arrangement to the 

 villi of the intestines. Arborescent means branched like a tree, and 

 plumose denotes a delicate feathery growth. 



When liquefaction occurs in the gelatin the liquefied zone is likely 

 to show very definite arrangements and shapes, to which the following 

 descriptive terms are applied: 



FIG. 89 



Showing characters of gelatin stab cultures: A, characters of surface elevation: 1, flat; 

 2, raised; 3, convex; 4, pulvinate; 5| capitate; 6, umbilicate; 7, umbonate. B, characters of 

 growth in depth: 1, filiform; 2, beaded; 3, tuberculate-ecinulate; 4, arborescent; 5, villous. 

 (From Chester.) 



Crateriform, a flat excavation like a saucer or crater. 



Tubular, cylindrical, saccate, elongated areas of liquefaction. 



Infundibular or conical, more or less funnel-shaped areas of lique- 

 faction. 



Fusiform or spindle-shaped, those which have the greatest diameter 

 in the middle and taper both upward and downward. 



In stratiform liquefaction the whole mass at the upper end of the 

 gelatin tube becomes fluid and the process progresses downward, 

 involving deeper and deeper strata of the culture medium. 



The liquefied gelatin may be comparatively clear, with a sediment 



