Darkfield illumination requires blocking out of the central light which ordinarily passes through and around (surrounding) the specimen, allowing only oblique rays from every azimuth to "strike" the specimen mounted on the microscope slide.
(Darkfield illumination; requires; blocking) (the central light; ordinarily passes; through and around; the specimen, allowing only oblique rays from every azimuth to "strike") (the specimen; allowing; only oblique rays from every azimuth to "strike" the specimen mounted on the microscope slide) (the specimen; mounted; L:on the microscope slide)
Darkfield illumination the central light the specimen the specimen
requires ordinarily passes allowing mounted
blocking
through and around the specimen, allowing only oblique rays from every azimuth to "strike"
only oblique rays from every azimuth to "strike" the specimen mounted on the microscope slide
L:on the microscope slide