Noninvasive observation of embryonic behavior in chicks using holographic interference

Laser holographic techniques offer a sensitive means of detecting small displacements. This paper describes the use of holographic interference to study the movements of an embryo in an intact incubating egg. The method is noninvasive and enables one to monitor the development of behavior in the chick embryo. Movements are displayed in the form of fringes on a TV screen and recorded on videocassettes as a function of time. This is the first report of the use of an optical interference phenomenon to detect movements of an embryo. Besides being useful in the study of the prenatal motility cycle, the method allows one to discriminate diverse types of movement, their onset, duration, and frequency of repetition. Examples are provided to illustrate some movements. The spectacular holographic aided visioning of the pipping behavior of the chick embryo is then briefly described.