Extirpation experiments upon the embryonic forelimb of the rat.

The technique of intrauterine surgery by which experimental methods may be applied to mammalian embryos has recently been described. 1 The results of a preliminary investigation show that rat embryos, operated within the last eight days of development, generally survive the operation, remain viable and are born with the rest of the litter. It is possible to rear such animals although it is difficult to do so.

The first point of attack to which this method is being applied is the study of the factors influencing limb development. The first phase of this problem, the capacity for regeneration, forms the basis of this communication.

The anesthetized pregnant animal is placed upon the operating table with the dorsum toward the operator. An incision is made extending from the costal line to the anterior margin of the hind leg, through the dorsal skin and musculature of the body wall. This admits the operator to a field in which the embryos are clearly visible through the uterine wall. This method of approach obviates excessive handling of the viscera and consequent operative shock.

The incision through the uterine wall is made just large enough to permit manipulation of the limb and its extrusion through the opening. The limb is then excised at the determined level by means of fine iridectomy scissors, ligature or cautery.