Technics for Avian Blood
Lack of satisfactory technics is one of the reasons why studies of avian blood have not been carried forward as energetically and successfully as have studies of mammalian blood. Students of avian hematology have found that they frequently get unsatisfactory results when they attempt to apply technics that are known to be suitable for studying the blood of mammalian species.
Over a period of years this Laboratory has modified a number of commonly used technics to suit the needs of avian hematology.
Perhaps the greatest deterrents to accurate and critical study are (1) lack of a good microscope, (2) lack of a good light source, and (3) deficiencies in setting up and using microscope and light.
Here is what one often finds in a laboratory: The "good" microscope is tucked away in a box. When a special occasion arises, it is brought forth and placed on a table close to a 75- or 100- watt bulb or a lamp with a frosted glass in front. Then the condenser is dropped below the level of the stage until the amount of light is right, or the diaphragm is closed so that the object shows up well.
For a quick look with low magnification, such procedure may be satisfactory, but efforts are often made to do critical studies under an oil immersion lens with this type of set-up. The efforts are disappointing because the microscope is prevented from giving top-quality performance.
Many good books have been written on the use of the microscope. Nevertheless it is not uncommon to see research workers, technicians, veterinarians, and physicians using the instrument as if there were no directions. Correct use is emphasized here not only because the authors hope that their comments may be helpful to other workers, but also because it is desired to assure the reader that the structures depicted in the illustrations have actually been seen in specimens. The reader who fails to locate, in specimens of his own, the small structural and tinctorial differences depicted here should not conclude that they do not exist; he should consider the possibility that he is not working under optimum conditions.
The information that follows was obtained from the late Dr. Max Poser of the home office of Bausch & Lomb Optical Co. and from Mr. H. L. Shippy of the Detroit office of that company. Similar information has been presented by Dr. Oscar W. Richards in Color and Illumination, published by the Spencer Lens Co. Two other useful reference items by Dr. Richards will be found in Literature Cited ( Richards, 1938 and 1949). Another reference ( Spitta, 1920) has provided particularly helpful explanations of the differences between achromatic and apochromatic lenses, and of why Huyghenian eyepieces should be used with the former and compensating oculars with the latter.
An ideal light source is a small, brilliant point of Light that is passed through a lens designed to produce parallel or nearly parallel rays. All the drawings in this Atlas were made with a tungsten arc light.
The lamp should be placed about 2 feet in front of the microscope and the image of the light source brought to a focus on a white card placed in front of the microscope mirror. Adjustments in focus can be made by moving the lamp condenser in and out. Just in front of the condenser lens of the lamp is a leaf diaphragm, which should be wide open at this stage of setting up the lamp and microscope. The next step is to place a clear blue daylight filter in one of the three slots in front of the lamp diaphragm. The slots are constructed to hold 2" x 2" filters. One. may purchase a good lamp capable of giving critical or Köhler illumination,1 then nullify its value by placing a ground glass in the path of the light.____________________