. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 354 bulletin: museum of comparative zoology. hundred milligrams of impure radium one thousandth as strong as the pure bromide was held in a tightly closed cell (Fig. 2) consisting of a glass floor 25 mm. square, sides of sealing-wax two millimeters high, and a roof consisting of a very thin mica window. The cell rested in a Petri dish of salt water. Pieces of the stem of the hydroid six tenths of a millimeter in diameter were laid upon the window. The quality of the radiations was constant for all the experim
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 354 bulletin: museum of comparative zoology. hundred milligrams of impure radium one thousandth as strong as the pure bromide was held in a tightly closed cell (Fig. 2) consisting of a glass floor 25 mm. square, sides of sealing-wax two millimeters high, and a roof consisting of a very thin mica window. The cell rested in a Petri dish of salt water. Pieces of the stem of the hydroid six tenths of a millimeter in diameter were laid upon the window. The quality of the radiations was constant for all the experiments, since this method of exposure was always employed. The alpha rays were cut off from the hydroid stems by the mica. The gamma radiations, were so weak as to be negligible. The pieces of stem were sixteen millimeters in length, of nearly equal diameter and from like portions of thrifty colonies. With hardly an exception they regenerated one hydranth. The pieces used as control received treatment like the others, except that the cell on which they were placed contained a non-radioactive yellow powder. The whole process of regenerating a hydranth was arbitrarily divided into eight stages for the purpose of numerically expressing the amount. Fig. 5.— Curves showing acceleration of hydranth regeneration due to 7 hours' exposure to the beta rays of radium. The units of the ordinate indicate per cent of development. The units of the abscissa indicate hours from time of cutting. The curve with the broken lines is based on control pieces. The curve with the continuous line is based on pieces exposed to radium. The bracket indicates the period of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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