ON THE LIMBS OF THE CHICK. 



the shell at the end of the forty-eighth hour of incubation, and 

 during the further development they were kept in porcelain cups 

 in a moist chamber. The latter method was found more prac- 

 ticable, as the first appearance and the subsequent growth of 

 the buds could be observed, and also the changes in the embryo 

 after the operation could be watched from time to time. 



The limb buds are not large enough for removal until the 

 beginning of the fourth day, and allowing for the delay in develop- 

 ment caused by the operation, at least four additional days of 

 incubation are needed before the wings and legs show marked 

 characteristics. At the end of the fourth day the embryo lies 

 on its left bide; for this reason the operations were made on the 

 right side. The buds were removed by means of a curved knife 



FIG. i. Two views of a chick on the seventh day. A, the right side showing 

 the stump of the wing W and the leg L with the line of the graft G. B, the normal 

 side. 



made by heating and bending a no. 12 cambric needle into a 

 hook and sharpening it at the curve. The hook was inserted 

 under the bud and drawn up quickly, thus removing the tip 

 with the least possible disturbance to the surrounding parts. 

 The buds were then carried on the needle to the position desired, 

 and held in place for a few minutes until they adhered. The 

 greatest difficulty was met with in the effort to keep the grafts 

 together. Some were fastened by fine glass threads, but this 

 was ot found satisfactory as the insertion of the thread tore the 

 tissues. In many of the embryos the grafts came apart, and the 

 buds floated in the albumen or sank in the yolk. Another dif- 



