Converse Relation between Ciliary and N euro-Muscular Movements. 19 



R. S. Lillie ^ found that pure solutions of potassium of 0.5 molecular 

 concentration are capable of long maintaining the activity of the cilia 

 of Arenicola larvae and Mytilus, and it is of interest to observe that such 

 strong concentrations of the potassium ion immediately depress neuro- 

 muscular movements without primary stimulation, thus acting upon 

 the neuro-muscular system in a manner the exact reverse of their effect 

 upon cilia. 



EFFECTS OF CALCIUM. 



Strong concentrations of calcium such as 0.5 molecular CaCl._j quickly 

 check ciliary movement in worm larvae, Veligers, and Ctenophores with- 

 out destro\dng the cilia. In Mytilus, however, according to Lillie (1906, 

 p. 130), ciliary movement may last for several hours. 



In weak concentrations, however, or if combined with NaCl, ciliary 

 activity continues much longer in calcium solutions than do the neuro- 

 muscular movements. We may conclude that calcium in combination 

 with sodium is a stimulant for the movement of cilia, for it prolongs the 

 duration and increases the rate of movement over and above that caused 

 by NaCl alone. 



The larvae of the palolo worm will swim slowly without an initial 

 stop for about half an hour in 0.625 molecular (looNaCl -1- 3CaCl2), 

 while Spirobranchus larvae will beat from 45 to 90 minutes, and Cteno- 

 phore cilia will vibrate with abnormal rapidity for from 6 to 30 minutes 

 in this solution, the coordination being in many cases destroyed, so that 

 each comb beats independently of its neighbors and the animal is unable 

 to progress despite the fact that its cilia are abnormally active. In this 

 connection it is interesting to observe that Lillie ^ finds that mechanical 

 stimulation arrests the automatic activity of the swimming-plates of 

 Ctenophores, but that this does not occur in the absence of calcium, and 

 the effect decreases as the calcium is decreased. 



Carlson, 1906,^ concludes that calcium depresses both the ganglia 

 and the muscles of the heart of Limulus without primary stimulation ; 

 and my studies of Cassiopea led me in 1908 * to a similar conclusion in 

 respect to this animal. Authorities differ in respect to the role played 

 by calcium in the pulsation of the vertebrate heart. We must remember 

 that calcium combines with sodium, forming a compound which offsets 

 the inhibitory effects of magnesium, and it appears to me that the so- 

 called stimulating effect of calcium is due to this secondary action, for 

 if sodium be absent calcium has no power to overcome the depressant 

 action of magnesium. In the case of Cassiopea, calcium augments the 

 rate of pulsation only if added to solutions containing sodium and 

 magnesium, and it is evident that this effect is due to its combining with 

 sodium, thus forming a compound which counteracts the depressant 

 effects of magnesium, not to any direct stimulating action of its own. 



^Lillie, R. S., 1902, Amer. Jour, of Physiol., vol. 7, pp. 46, 52; also, Ibid., 

 1906, vol. 17, p. 93. 



^Lillie, R. S., 1908, Amer. Jour. Physiol., vol. 21, pp. 200-220. 



^Carlson, 1906, Amer. Jour. Physiol., vol. 16, pp. 390, 394. 



■♦ Papers from the Tortugas Laboratory of the Carnegie Institution of Wash- 

 ington, vol. I, 1908, pp. 115-131. 



