276 Eegeneration of the Skin of the Frog 



The solution and the tap water for all these series were changed every 

 day for the first week and every other day thereafter. At the end of 

 periods varying from ten hours to five weeks, frogs were killed and the 

 tissue about the wounds removed. 



Corrosive-acetic was used for fixing and the material was embedded in 

 celloidin. Serial sections were made and stained in Delafield's hema- 

 toxylin and eosin. Altogether, series of sections from 62 frogs were 

 examined.^ 



Observations. — No constant effects on regeneration have been noticed 

 for the atropine and pilocarpine solutions used. Regeneration of both 

 epithelium and connective tissue seemed to take place equally well in 

 either the weaker atropine, the pilocarpine solutions, or the tap water. 

 There was no marked difference in the number of mitoses when these 

 solutions were used. In some cases there was a little evidence of pos- 

 sibly greater activity in regeneration, for some cases, in the pilocarpine 

 solution than in the atropine. This difference was very slight and 

 possibly accidental. In one series of experiments the number of leuco- 

 cytes immigrating into the woimd was decidedly larger in the pilocarpine 

 solutions. This difference, however, was not observed in a second series. 

 Frogs kept in either the weaker or the stronger solutions of pilocarpine 

 did not behave differently from those in tap water, even at the end of 

 four or five weeks; they were nearly all equally active. The animals 

 placed in the stronger atropine solution were very stupid and helpless 

 at the end of the first day or two, apparently being partially paralyzed, 

 and none lived longer than five days. The weaker solution seemed to 

 have a somewhat similar but much milder effect in a few cases. 



In the former series of experiments carried out in the spring of 1901, 

 and referred to above, tadpoles, whose tails had been cut, were kept in 

 1-6 per cent solutions of alcohol and in weak chloroform water up to 

 six days after the operation; the control animals lived in tap water. 

 These experiments were undertaken in order to ascertain whether or 

 not these narcotic substances delay and weaken the movements and the 

 growth of the cells. No marked differences in regeneration were ob- 

 served between the different sets of tadpoles, with the possible exception 

 of slight differences in the rapidity with which the epithelium covered 

 the wound. 



Regeneration of the Epidermis. — Barfurth, 91, observed in the Sala- 

 mander a rapid movement of epithelium over a wound before any in- 



^ A part of these investigations was carried on with the aid of a grant 

 from the Research Fellowship Fund of McGill University. 



