574 STUDIES IN GENERAL PHYSIOLOGY 



of rhythmical contractions. In this case the addition of Ca 

 ions to a pure NaCl solution will produce rhythmical activity. 

 In a former paper I have shown that skeletal muscle can be 

 caused to beat rhythmically if we increase the number of its 

 Na ions without increasing the number of its Ca ions. In 

 one of the next papers it will be proved that the same result 

 can be obtained more rapidly if we decrease the number of 

 Ca ions in the muscle by precipitating them. 



3. The phenomena of muscular contractility and the phe- 

 nomena of cell-division are considered by many authors as 

 being of the same order. The rays of the astrosphere are 

 said to be contractile fibrils which pull the chromosomes 

 apart and accomplish the division of the mother-cell into 

 two daughter-cells. I do not see how we can harmonize 

 this hypothesis with the fact that enormous quantities of K 

 ions in no way interfere with the process of karyokinesis, 

 while even a much smaller amount of K ions annihilates 

 muscular activity in a very short time. In the preceding 

 paper I mentioned the fact that the ciliary motion of the 

 blastulse of the sea-urchins continues in the presence of enor- 

 mous quantities of K ions. The riddle of contractility is 

 still unsolved. It yet remains to be proved that the ciliary 

 motion and cell-division are due to contractile processes 

 identical with those in the muscle. Our experiments on the 

 effects of K ions should warn us against taking such an 

 identity for granted. 



4. While a solution of NaCl with a small amount of K and 

 Ca ions allows all the various vital processes to go on (except 

 such special phenomena as the formation of the skeleton, 

 with which we shall deal in the next paper), we find other 

 combinations of ions which enhance some of the vital pro- 

 cesses, while they prevent others. The most important com- 

 bination in this direction is the mixture of ^n KC1 with a 

 small amount of \n CaCL. In such a solution the first 



