. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 208 PHILIP H. ABELSON AND WILLIAM R. DURYEE thus re-checked to insure that the plane of section was being made parallel to the egg axis. Improperly oriented eggs were discarded. Subsequent slices through the lateral third of the nucleus were made, making the surface even and parallel with the bronze strip. The nucleus always stood out sharply as a white circle in a grey background of frozen cytoplasm. Finally the strip was inverted and the cell was sectioned similarly from the other side. Frozen sections were conveniently te
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 208 PHILIP H. ABELSON AND WILLIAM R. DURYEE thus re-checked to insure that the plane of section was being made parallel to the egg axis. Improperly oriented eggs were discarded. Subsequent slices through the lateral third of the nucleus were made, making the surface even and parallel with the bronze strip. The nucleus always stood out sharply as a white circle in a grey background of frozen cytoplasm. Finally the strip was inverted and the cell was sectioned similarly from the other side. Frozen sections were conveniently temporarily stored in a cold slotted brass holder in an insulated box, cooled with solid FIGURE 2. Brass cooling block for holding frozen egg and supporting strip during section- ing. Note that both holes corresponding to eggs in holder are displaced laterally from the main axis of the block, so that the strip, when inverted after first sectioning, brings cut surface against flat portion of the block. Screw at each end makes convenient attachment for handle. Actual exposure of the section to film took place in a well-insulated chest fitted with a copper bottom and copper slide holder. One hundred pounds of dry ice kept the temperature in the slide holder at approximately - 40° C. for a week. Medium-contrast lantern slide plates 1 were laid in the slide holder, emulsion side up, and the cold bronze strips with the frozen sections were laid on the plates, being weighted to insure even contact. With the activity of our solutions, it was found necessary to expose from two to twelve hours to provide the desired darken- ing. Plates were developed in Eastman D-19 developer. A typical calculation indicates the amounts of radioactivity involved. A section of a frog egg 80 ^ thick contained X 10~s g. of exchanged sodium. This sample 1 We have learned from Dr. Kenneth Endicott, of the National Institutes of Health, that Ansco non-screen X-ray films are particularly useful where o
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
