benson's microbiological applications laboratory manual in general microbiology - alfred e brown

[...]... microscope with one of them If it is necessary to insert an ocular micrometer in your eyepiece, find out from your instructor whether it is to be inserted below the bottom lens or placed between the two lenses within the eyepiece In either case, great care must be taken to avoid dropping the eyepiece or reassembling the lenses incorrectly Only with your instructor’s prior approval shall eyepieces be disassembled... and other types of transparent cells Figure 3.1 illustrates the differences between brightfield and phase-contrast images Note the greater degree of differentiation that can be seen inside cells when they are observed with phasecontrast optics In this exercise we will study the principles that govern this type of microscope; we will also see how different manufacturers have met the design challenges of... result When these lamps are cold they are relatively safe, but when hot, the inside pressure increases to eight atmospheres, or 112 pounds per square inch The point to keep in mind is this—never attempt to inspect the lamp while it is hot Let it cool completely before opening up the lamp housing Usually, 15 to 20 minutes cooling time is sufficient 2 Never expose your eyes to the direct rays of the... microscope from the cabinet at the beginning of the period, you expect it to be clean and in proper working condition The next person to use the instrument after you have used it will expect the same consideration A few moments of care at the end of the period will ensure these conditions Check over this list of items at the end of each period before you return the microscope to the cabinet 1 Remove the slide... the energized molecules, the phenomenon is referred to as photoluminescence In photoluminescence there is always a certain time lapse between the absorption and emission of light If the time lag is greater than 1/10,000 of a second it is generally called phosphorescence On the other hand, if the time lapse is less than 1/10,000 of a second, it is known as fluorescence Thus, we see that fluorescence... passes up through the instrument to the eye Some general principles related to its operation will follow an explanation of the principle of fluorescence THE PRINCIPLE OF FLUORESCENCE It was pointed out in the last exercise that light exists as a form of energy propagated in wave form An interesting characteristic of such an electromagnetic wave is that it can influence the electrons of molecules that... are pressurized and can explode Another hazard exists in direct exposure of the eyes to harmful rays Knowledge of these hazards is essential to safe operation If one follows certain precautionary measures, there is little need for anxiety However, one should not attempt to use one of these instruments without a complete understanding of its operation Heat Filter The infrared rays generated by the mercury... red algae, are not usually encountered in freshwater ponds, they have not been included here Division 1 Euglenophycophyta (Euglenoids) Illustrations 1 through 6 in figure 6.2 are typical euglenoids, representing four different genera within this relatively small group All of them are flagellated and appear to be intermediate between the algae and protozoa Protozoanlike characteristics seen in the euglenoids... converge on the phase ring to be advanced or retarded 1⁄4 wavelength These rays emerge as solid lines from the object on the slide This ring on the phase plate is coated with a material that will produce the desired phase shift The diffracted rays, on the other hand, which have already been retarded 1/4 wavelength by the phase object on the slide, completely miss the phase ring and are not affected... © The McGraw−Hill Companies, 2001 Phase-Contrast Microscopy • Exercise 3 are rigidly set and needn’t be changed unless someone inadvertently disturbs them To observe ring alignment, one can replace the eyepiece with a centering telescope as shown in figure 3.7 With this unit in place, the two rings can be brought into sharp focus by rotating the focusing ring on the telescope Refocusing is necessary . lab- oratory safety, three new features have been incorpo- rated into the text. In addition, several experiments have been altered to improve simplicity and reliability. The three exercises that. test tubes, follow the pro- cedures outlined in Exercise 8. Inoculating loops and needles should be heated until they are red-hot. Before they are introduced into cultures, they must be allowed to. transparent cells. Figure 3.1 illustrates the differ- ences between brightfield and phase-contrast images. Note the greater degree of differentiation that can be seen inside cells when they are observed