In the literature of pathology there are many cases described in which parts of the body of mammals, particularly internal organs, have been grafted in unusual regions. The results have not always been the same, for while in some cases it appears that the operation has succeeded, in others the grafted part is subsequently absorbed, and in still other cases the graft may be at first partly absorbed and later begin to grow again. It appears that the establishment of an adequate blood supply is the most important element of success. Ribbert, who has made an extensive and successful series of experiments, has stated that the grafting takes place better when small pieces of an organ are used, since these can draw immediately on the surrounding regions for their oxygen, etc., while larger pieces are found to break down in the interior, owing to the fact that this part is too far removed from the supply of oxygen, food, etc. After the grafted piece has established a blood supply of its own, it may continue to grow. Ribbert transplanted small pieces of different tissues of the rabbit and guinea pig in, and upon the surface of, the lymph glands of the same or of another individual. The lymph gland was chosen because small pieces of tissue can be afterwards easily detected. A small piece of tissue about as large as a pin’s head is cut off from whatever tissue is to be grafted, and as quickly as possible placed in a small cleft made in the lymph gland. After several days, weeks, or months, the gland is removed and the graft examined by means of serial sections. Most of the experiments were made with “epithelial organs,” and according to Ribbert, if pieces of such organs are composed of epithelium only, they cannot be successfully grafted. For instance, the cells of the cornea can be readily separated from their underlying connective tissue, and can be kept alive in the lymph gland, but the cells diminish in number, show retrogressive metamorphosis in the direction of atrophy, and are finally absorbed. It seems that epithelium by itself cannot extract nourishment from its surroundings. Nothing is easier, however, than to transplant epithelium, if its connective tissue is present. The connective tissue furnishes so good a basis for nourishment that the epithelium not only lives, but may continue to proliferate. Ribbert finds that pieces of skin roll in after their removal. Then a process of growth takes place corresponding to that which follows a wound in the skin. The surface is closed and a small cyst is formed with a central cavity. The epithelium undergoes no changes during the first days or weeks. It remains stratified and shows an active process of cornification and desquamation. Similar results were obtained when pieces of the conjunctiva were transplanted, either under the skin in the anterior chamber of the eye, or in the lymph gland.