ON EEGENEEATIOX IN THE PIGMEXTED SKIN OF THE 



FEOG, AND ON THE CHAEACTEE OF THE 



CHEOMATOPHOEES. 



BY 



LEO LOEB AND R. M. STRONG. 



From the J. R. H. Molson Laboratories of Pathology and Bacteriology, 

 McGill University, Montreal. 



In a former paper L. Loeb, 97, described the changes occurring in 

 the pigmentation of regenerating black skin on the ear of the guinea- 

 pig, and after transplantation of pigmented skin into white skin. In 

 this paper we give the results of a study of the conditions in regenerat- 

 ing 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 inves- 

 tigating the influence of different substances upon the growth of tissues 

 in higher animals. In earlier experiments one of us (Loeb) had inves- 

 tigated the influence of narcotic substances like alcohol and chloroform 

 upon the regeneration of the tail in tadpoles. In these experiments 

 atropine and pilocarpine were chosen, because Matthews, 02, had more 

 recently found that pilocarpine accelerates the development of fertilized 

 ova of Asterias somewhat. 



Metliods and Material. — 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 I-IV2 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 sul- 

 phate 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. 



American- Journal of Anatomt.^Vol. III. 



