Manual of basic techniques for a health laboratory - libdoc.who.int

5. Bacteriology 2115.6.3 Microscopic examinationExamine the slide using the dark-field microscope.With experience of dark-field microscopy, the treponemes may be seen and can bedistinguished from saprophytic treponemes by their size, characteristic movementand typical number of coils (Fig. 5.26).Fig. 5.26 Treponemes5.7 Examination of semen specimensSemen is investigated in patients to exclude infertility. This is done by assessing thefunctional characteristics of spermatozoa in the seminal fluid.5.7.1 Materials and reagents●●●●●●●●●●MicroscopeMicroscope slidesCoverslipsBlood (Sahli) pipetteGraduated cylinder, 10mlpH indicator paperImproved Neubauer counting chamberSodium bicarbonatePhenol or formalin (37% formaldehyde)Distilled water● Petroleum jelly.Before collecting the semen specimen, prepare the semen diluting fluid asfollows:— sodium bicarbonate 5 g— phenol or formalin 1 ml— distilled water to 100 ml.