THE INHIBITIVE ACTION OF THE ROENTGEN 



RAYS ON REGENERATION IN 



PLANARIANS. 



BY 



CHARLES RUSSELL BARDEEN, M. D., 



Associate Professor of Anatomy, the Johns Hopkins University, Baltimore. 



AND 



F. H. BAETJER, M. D., 

 Director of the Roentgen Apparatus, the Johns Hopkins Hospital, Baltimore. 



The great capacity of regeneration possessed by fresh-water 

 planarians is well known because of the number of investigations 

 lately devoted to the subject.^ Complicated portions of the body, 

 like the head and pharynx, when removed, are restored within a 

 few days or weeks. In several species a new individual may 

 be regenerated from a very small, isolated piece. We have found 

 that this power of regeneration may be completely destroyed by 

 exposing planarians to the action of the Roentgen rays. 



Our experim.ents have been conducted upon two species of 

 planarians which have especial regenerative capacity, P. maculata 

 and P. lugubris.. Specimens were placed in shallow, open dishes 

 about ten to fifteen centimeters below the vacuum tube and were 

 exposed from ten to twenty minutes each day for varying periods 

 of time. We made use of a twenty-centimeter coil with an inter- 

 rupter of the electrolytic type, a ten-Inch coil with a mechanical 

 Interrupter, and several styles of vacuum tubes. The vacuum of 

 each tube was so arranged that rays of "medium-soft" quality 

 were obtained. 



1 In addition to the literature quoted in Morgan's "Regeneration," New York, 

 1901, articles have appeared as follows: F. R. Lillie, American Journal of 

 Physiology, VL, p. 129, 1901 ; E. Schultz, Zeitschrift f. wissenschaftliche Zo- 

 ologie, LXXII, p. I, 1902; N. M. Stevens, Archiv. f. Entwichelungsmechanilk 

 XIIL, p. 396, 1901 ; T. H. Morgan, Archiv. f. Entwichelungsmechanik, XIIL, p. 

 179, 1901 ; Biological Bulletin IIL, p. 132, 1902 ; H. F. Thacher, American Nat- 

 uralist, XXXVL, p. 633, 1902; C. R. Bardeen, Biological Bulletin III., 262, 1902; 

 Archiv. f. Entwichelungsmechanik, XVP., p. i, 1903. 



