Experimental Production of Atrophied and Partly Deficient Limbs (Phocomelias) in the Axolotl Embryo

1. The results obtained indicate the development of some types of atrophied and locally deficient limbs as related to the method applied. 2. The larvae operated after method 3 (implantation along a vertical line) show the implanted ectoderm still attached along the radial border of the operated limbs (figs. 5 and 6). The length of these limbs is half as long as normal and the distal ends show rudiments of fingers, the number of which is reduced. 3. The length of the limbs, the primordia of which were operated after method 2 (superficial implantation), was always normal, but the digits of those limbs are either deformed (case 999) or they show the implanted ectoderm replacing a digit (case 983) or they possess an abnormal number of digits or some of the digits are abnormally long (case 1009). 4. All cases developing after application of method 1 (deep implantation) showed abnormally short and atrophied limbs. The type of deformity developing after this method is the so-called phocomelias. In the phocomelias the proximal parts of the limb are essentially reduced in length and the distal parts show normal or slightly reduced lengths of the digits. 5. Phocomelias is not uncommon in the human newborn and it is considered as a deformity developing on a genetical basis. It has not yet been proved that phocomelias can be produced experimentally by non-genetical methods. We can conclude from the experimental method applied that the ectoderm implanted into the deep area of the embryonic primordium of the limb bud acts as a factor preventing the normal efficiency of developmental potencies.