. The microscope : an introduction to microscopic methods and to histology. Microscopes. PHO TO-MICROGRAPHY [CH. VIII. Bi-EITTi IWl li HtWI Ill-unit^ â ^ ; 1 < g. ""â §281. Arranging the Embryos.âAs usually prepared the embryos are white and therefore require a dark background. This may be attained either by placing the embryos in a dark dish or on some paper blackened with water-proof India ink, or by putting them in a glass vessel like a Petri dish with a piece of black velveteen on the stage below. Black glass on the bottom of the dish containing the embryos etc., forms one of
. The microscope : an introduction to microscopic methods and to histology. Microscopes. PHO TO-MICROGRAPHY [CH. VIII. Bi-EITTi IWl li HtWI Ill-unit^ â ^ ; 1 < g. ""â §281. Arranging the Embryos.âAs usually prepared the embryos are white and therefore require a dark background. This may be attained either by placing the embryos in a dark dish or on some paper blackened with water-proof India ink, or by putting them in a glass vessel like a Petri dish with a piece of black velveteen on the stage below. Black glass on the bottom of the dish containing the embryos etc., forms one of the best dark backgrounds. The specimens will of course be in a liquid, usually alcohol. Fig. 167-178. Leitz Micro- summar Objectives of 64 and 42 mm. focus. {Cuts from Leitz Photomicrographic catalog). If several embryos are to be taken at once, they are arranged in rows something as the. words on a line. Arrange them in even vertical as well as horizontal rows so that when the print is made it will be easy to cut them apart. When the embryos are arranged, one should be certain that the light brings out the details most desired. For example, if one is photographing an embryo which shows the branchial pockets well, great pains should be taken to so arrange the embryo with reference to the light that the proper shading will be given to bring out the gill pockets most emphati- cally. One can learn to do this only by practice. It is advanta- geous to have an assistant, then while the operator is, looking into the camera the assistant can turn the embryo in various directions until the appearance is most satisfactory. § 282. Focusing.âFor getting a general focus, and for the general arrangement the ground glass screen is used, but for the final focusing it is desirable to use a focusing glass. The tripod microscope answers fairly well for a focusing glass, but several are now made with much more perfect corrections and for photo-micrography it is desirable to have as good
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