20 LABORATORY BACTERIOLOGY 
do the individual bacteria move from one point in the field 
to another? To determine this the center of the drop is 
better. Clearly distinguish between genuine motility and a 
simple dancing motion (the Brownian movement). Deter- 
mine the presence or absence of spores. These are bright, 
highly refractive bodies either within or outside the bodies 
of the bacteria. If present, they can usually be seen in both 
positions. Is there any evidence of a capsule around the 
bacteria ? 
31. Chester’s terminology for descriptive bacteriology. Ches- 
ter has introduced a terminology in descriptive bacteriology 
which has the advantage of being definite and concise, while 
at the same time it is sufficiently elastic to fit the varying 
=o oe 
— aN f_\ 
1 2 3 4 by) 
Fic. 1. Characters of surface elevation: 1, flat; 2, raised; 3, Convex; 
4, pulvinate; 5, capitate; 6, umbilicate; 7, umbonate. 
forms of growth. It applies to the surface growth, to the growth 
along the needle track in the depth of the media, and to 
colonies on plate cultures. 
1. Surface elevation. General character of surface growth as 
a whole. 
Flat: thin, leafy, spreading over the surface. 
Effused: spread over the surface as a thin, veilly layer, 
more delicate than the preceding. 
Raised: growth thick, with abrupt terraced edges. 
‘Convex: surface the segment of a circle, but very flatly 
convex. 
Pulvinate: surface the segment of a circle, but decidedly 
convex. 
Capitate: surface hemispherical, 
