. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 260 R. WICHTERMAX AXD F. H. J. FIGGE cc. of culture medium above and below was omitted (Fig. 1, C). Both sets of boxes were irradiated with 170 kr. This dose killed all of the paramecia in the drops in both boxes. All of the paramecia in the one cc. of culture fluid in the inverted lids survived. In the case of the paramecia in the inverted lid on top of the box (uncovered and exposed to the atmospheric oxygen at the surface of the culture medium), survival was 100 per cent. Thus it was apparent that all the paramecia in the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 260 R. WICHTERMAX AXD F. H. J. FIGGE cc. of culture medium above and below was omitted (Fig. 1, C). Both sets of boxes were irradiated with 170 kr. This dose killed all of the paramecia in the drops in both boxes. All of the paramecia in the one cc. of culture fluid in the inverted lids survived. In the case of the paramecia in the inverted lid on top of the box (uncovered and exposed to the atmospheric oxygen at the surface of the culture medium), survival was 100 per cent. Thus it was apparent that all the paramecia in the drops in the plastic container were killed even though they wrere partially shielded by two cc. of culture fluid (one cc. above and one cc. below). Because of this differential sensitivity resulting from differences in the degree of exposure of the culture medium to air, the plastic boxes and hanging drops were abandoned and the Nylon syringes were utilized as x-radiation chambers for the reasons given earlier. The irradiation of paramecia in the syringes (which con- tained no air bubbles ) yielded results that were much more uniform. Using the syringe method, the results of seven experiments involving nine different dosage groups and 36 determinations are shown in Table I and the survival curve of Fig- ure 4. In the Xylon syringes, most of the paramecia survived a dose of 170-212 kr. (lethality := 5-6 per cent). As this dosage is exceeded, however, the per cent of animals that survive 24 hours after irradiation takes a sharp drop. Generally no animals survived a 510 kr. dose. 100- 90- 80- 70- 60- 50- 40- 30- 20 H 10 - X-RAY SURVIVAL CURVE FOR PARAMECIUM. 170 255 DOSE IN KR. 340 425 510 FIGURE 4. X-ray survival curve for Paraincciiuii caudatnin irradiated in Nylon syringes. This curve is based on seven experiments and after irradiated paramecia were observed for 24- hour period after expulsion from Nylon syringes. Coincident points are not indicated. Each point represents obse
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
