The role of movement in the development of joints and related structures: the head and neck in the chick embryo

Skeletal muscle contractions are necessary during embryonic life for the normal development of joints. The general features of joint development in immobile limbs were first studied with the techniques of grafting and organ culture. (Murray, 1926; Murray & Selby, 1930; Fell, 1925; Fell & Canti, 1934; Hamburger & Waugh, 1940; Lelkes, 1958). However, these methods of necessity entail a drastic alteration in the environment of the developing articulations, which may result in gross distortions of the skeletal structures themselves. More recently, neuromuscular blocking agents have been used to produce paralysis of chick embryos in ovo. When administered intravenously, these pharmacological substances produce profound paralysis, which may be continued for prolonged periods during embryonic development (Drachman & Coulombre, 1962a, b).