244 STUDIES IN GENERAL PHYSIOLOGY 



No regeneration whatsoever occurred in the first solution; 

 in the second small abnormally formed polyps with tiny 

 tentacles, which soon dropped off, developed. No growth 

 occurred. 



5. Whether other substances can be substituted for NaCl 

 I was not able to investigate at this time. If we omit this salt 

 from our conclusions, our experiments show that a small 

 amount of potassium must be contained in solution if the 

 polyps are to regenerate, but that for the formation of normal 

 polyps and for normal growth magnesium is also required. 

 Besides NaCl (for which substitutes may perhaps be found), 

 these two substances suffice for regeneration and growth in 

 Tubularia. 1 In only one respect did the parts regenerated in 

 my artificial solutions differ from those obtained in normal sea- 

 water the periderm of the former remained soft, while that 

 of the latter became hard. The importance of potassium 

 in the formation of cells has been emphasized by Hoppe- 

 Seyler : 



Even though definite compounds of potassium with organic 

 substances which might be considered essential to life-processes 

 are unknown, the presence, without exception, of potassium in all 

 organisms from the lowest to the highest compels us to assume that 

 compounds of this metal play a necessary role in all general devel- 

 opmental processes. The organs of the invertebrates also always 

 contain potassium, and those parts of plants contain the greatest 

 amount of potassium which have the greatest developmental pow- 

 ers. The power of organisms to separate from and retain the 

 potassium of the liquids which nourish them is shown especially 

 well by the fact that fresh-water streams and lakes and sea-water 

 contain only very small amounts of potassium beside much larger 

 amounts of sodium, calcium, and magnesium, yet organisms grow- 

 ing in them contain much potassium, which they have been able to 

 collect only from these waters which are so poor in potassium, and 

 from nowhere else. 2 



1 This is not correct. The Serino water contains Ca which is also necessary for 

 regeneration. [1903] 



2 Physiologische Chemie, p. 61. 



