Rosenbruch, M. Early Chick Embryos - A Pain-Free System in Biomedical Research. IN: The Ethics of Animal Experimentation. Ed. Philip N. O'Donoghue. Pgs. 267-269. 1998.

Chick embryos have been a well-established test system in general and applied biochemical research for more than a hundred years - for example, in toxicology several methods exist for the study of teratogenic and irritant effects of test substances. The majority of applications use chick embryos during the second half of the incubation period, but even during the first 7 days of incubation this test system can be used to study effects on the embryos and/or on the extra-embryonic membranes. Examples of the application of the 'early chick embryo' test system in experimental biomedical research are given here. Irritative potential is evaluated by the topical application of the test substance on one half of the yolk-sac blood vessel system. Subsequently hyperaemia, haemorrhage or coagulation occur in this area and are recorded semi-quantitatively to give substance- and dose-dependent data (Rosenbruch & Holst 1990).