Converse Relation between Ciliary and N euro-Muscular Movements. 21 



In a 0.625 molecular lithium chloride solution the cilia of Spiro- 

 branchus cease instantly, but do not dissolve, whereas they both cease 

 at once and dissolve in a molecular dextrose solution in water. 



SUMMARY. 



Among the cations of sea-water sodium is the most potent inhibitor 

 of ciliary activity and the most powerful neuro-muscular stimulant. 



On the other hand, magnesium is the most potent in maintaining 

 ciliary movement and the most powerful inhibitor of neuro-muscular 

 movements. 



Potassium in weak concentration is a primary depressant for cilia, 

 but afterwards ciliary action recovers in its presence. For neuro- 

 muscular movements, however, it is at first a stimulant and finally a 

 depressant. 



Calcium is a weak stimulant for ciliary movement, but a depressant 

 for neuro-muscular activity. 



Ammonium at first stops and finally permits the recovery of ciliary 

 movement, but it at first stimulates and afterwards inhibits neuro- 

 muscular movements. 



Weak acids (H ion) at first depress and afterwards permit recovery 

 of ciliary movement, but they at first stimulate and afterwards depress 

 neuro-muscular movement. 



In each case the effect of the solution is exerted through its cation, 

 and among these cations whatever stimulates cilia depresses muscular 

 activity and whatever inhibits muscular movement stimulates cilia. 

 In nature the more highly specialized cilia, which are under the control 

 of the neuro-muscular system, stop whenever the muscles contract, and 

 beat only when the muscles are relaxed. This is well illustrated in the 

 combs of Ctenophores, the cilia of the lobes of Veligers, or the ciliated 

 bands of Trochophores, and Semper's larva. 



At times the trochophore larva of Spirobranchus does not contract 

 as a whole, but only a small sector of muscles underlying the peristomial 

 ring of cilia contracts. In this case the cilia overlying the contracted 

 sector immediately stop but the impulse which produces the "wheel 

 movement" of the ring of cilia passes over the inert cilia without affect- 

 ing them, so that the cilia of the uncontracted parts of the ring maintain 

 their normal movement. This accords with Parker's 1 observation that 

 cooling a part of the length of a row of ciliated plates in Ctenophores 

 stops the combs over the cooled area, but does not inhibit the trans- 

 mission of the wave impulse across this area. Kraft obtained similar 

 results in his experiments upon the ciliated epithelium of vertebrates. 2 



We may present the results of this paper in a graphic manner if we 

 represent a stimulus by a + sign and an inhibition of movement by a - 

 sign. Successive effects may be represented by a succession of signs; 

 thus, + means a depression followed by recovery of movement 

 and + an initial stimulus followed by depression. Bearing this 



1 Parker, G. H., 1905, Journal Experimental Zool., vol. 2, p. 417. 



2 Kraft, H., 1899, Pfliiger's Archiv fur ges. Physiol., Bd. 47, pp. 196-235. 



