The Effects of X-Rays on the Developing Chick

Abstract

Introduction DURING the course of the investigation of the effects of roentgen rays on the origin and development of the gonads in the chick, certain developmental anomalies and malformations have appeared in the material studied. It became apparent that such irradiation had affected the vitality and hatchability of the eggs, and that further study was indicated. The results of these observations constitute the material of this paper. Apparatus The x-ray machine used was mechanically rectified and provided with a Landauer roentgenometer. A Universal Coolidge therapy tube was used. The set-up of the machine for the entire experiment was as follows: The kilovolt meter was set at 96, which delivered 112 peak kilovolts as measured by the sphere gap; the milliammeter was set at 6 milliamperes; the focal distance was 10 inches; the filter was equivalent to 4 mm. aluminum; the roentgenometer was kept at 3.2 microamperes, which, by calculation, gave 0.6 r per second. The desired r, or dosage, was obtained by varying the time of exposure. A specially designed irradiation box was used for this experiment. In it was incorporated a portable incubator, a candler, and a scattered-ray absorber. An electrically heated incubator was used for this work. It was provided with a reliable thermostat, humidity equipment, and a means of ventilation. The temperature was kept at 103° F., with a variation less than 0.2° F., the humidity being kept at 50 to 60 per cent. The eggs were turned twice in 24 hours. Material and Methods Eggs of white and brown Leghorn chickens were used for this experiment. All were incubated for a certain period of time before they were irradiated. The age of the embryo varied from 19 to 243 hours incubation. The vitality of all eggs was established with the aid of the candler before irradiation. Controls were kept for each experiment. With the exception of irradiation, the control eggs were subjected to identically the same treatment as were the experimental eggs. In the early part of the experiment it seemed necessary to determine the effect of the shell and shell membranes on the x-rays. Out of the total of 572 eggs, 63 were irradiated through a window cut in the shell and its membranes. After irradiation, the opening was sealed and the eggs incubated. The rest of the eggs were x-rayed with their shells intact. Another attempt was made by measuring the rays of known amount with a Victoreen r-meter after they had passed through the shell and the shell membranes. The results will be discussed later in the paper.