On regeneration in the pigmented skin of the frog, and on the character of the chromatophores

In a former paper L. Loeb, 97, described the changes occurring in the pigmentation of regenerating black skin on the ear of the guineapig, and after transplantation of pigmented skin into white skin.I n this paper we give the results of a study of the conditions in regenerating frog skin.We shall consider principally the chromatophores and their origin in the epidermis, and add some notes on histological changes involved in the regeneration.We also give a brief statement of the results of some experiments with atropine and pilocarpine solutions.These later experiments were undertaken with the intention of investigating the influence of different substances upon the growth of tissues in higher animals.In earlier experiments one of us (Loeb) had investigated the influence of narcotic substances like alcohol and chloroform upon the regeneration of the tail in tadpoles.I n these experiments atropine and pilocarpine were chosen, because Matthews, 0 2 , had more recently found that pilocarpine accelerates the development of fertilized ova of Asterias somewhat.Methods and MaterkL-A patch of skin, 5-8 mm.long and 3-5 mm.broad, usually elliptical, but sometimes oval in outline, was removed from a black area on the dorsal surface of the left shank of each frog.The animals were in apparently good condition and mostly very active.Before operation they were kept at the laboratory for several days in large battery jars containing water about 1-1% inches deep.After the removal of the patch of skin, the frogs were divided into three series and placed in jars.The animals of one series were in jars containing tap water; another series was given a solution of atropine sulphate and a third lot of frogs had a solution of pilocarpine hydrochlorate.Both solutions had one part of the salt to 10,000 parts of water.A few animals also were placed in solutions of 1-1000 strength.