Alteration in Size of the Heart of Late Chick Embryos after Incubation at Varied Temperatures

Abstract

WE have observed a consistent alteration in the size of the heart of chick embryos following the exposure of 11- or 12-day-old embryos to increased or reduced temperatures of incubation for one week. In one series, ninety 11-day-old embryos, which had been maintained at the normal temperature of 37.5° C, were removed from their incubator, candled, and divided into three groups of 30 each. One group was placed in an incubator at 32.5° C, the second returned to 37.5° C, and the third placed at 42.5° C. On the eighteenth day of incubation live embryos were found as follows: 26 at 32.5° C, 29 at 37.5° C and 18 at 42.5° C. All the embryos at 42.5° C and 20 of the embryos from each of the other two groups were examined. The embryo was removed from its extra-embryonic attachments and weighed. The heart was removed with the great vessels cut close to the heart, and the organ weighed. The weights of each embryo and its heart are seen tabulated in Fig. 1.