Converse Relation hetiveen Ciliary and N euro-Muscular Movements. 11 



nal Physiol., vol. i6, pp. 386-395);^ Bethe's - studies on the effects of 

 these ions upon Rhizostoma pulmo also show that this medusa behaves 

 as does Cassiopea. 



This similarity of behavior suggests that the stimulus which pro- 

 duces rhythmical or other neuro-muscular movements in all of these 

 forms is of one and the same nature in each and all of them. It appears 

 that a slight excess of sodium maintained at the ganglionic centers causes 

 the nervous stimulus which produces pulsation in the medusa Cassiopea,^ 

 but I am unable to state what may be the normal cause of movements 

 in the other animals experimented upon in this research. In both 

 Cassiopea and the Annehds, however, o.i per cent oxahc acid in sea-water 

 quickly produces a permanent paralysis of the central nervous system, 

 leaving the muscles still capable of contracting locally under the influence 

 of stimuh, such as the touch of a crystal of postassium sulphate, although 

 the contraction spreads only in a slow myogenic manner from the stimu- 

 lated point. 



Moreover, in both the medusas and the worms, if the animals be in 

 sea-water and a small amount of a solution of 4 parts of sodium oxalate 

 in 1 ,000 parts of sea -water be allowed to diffuse locally upon them from 

 a pipette, movements wholly natural in appearance arise from the stimu- 

 lated area and spread over their bodies. These experiments do not prove 

 that the cause of movement is due to a slight excess of sodium at the 

 ganglionic centers in these invertebrates, but they suggest that this is pos- 

 sible. It will indeed be remembered that Parker and Metcalf , 1906 (Amer- 

 ican Journal of Physiol., vol. 17, pp. 55-74), found that the earth-worm 

 reacts vigorously to 0.002 molecular CaCl, responding to the cation, 

 and that it is more sensitive to sodium than to ammonium, lithium, or 

 potassium. 



Also Carlson finds that sodium chloride isotonic with sea-water 

 gives a primary augmentation to the ganglionic rhythm of the Limulus 

 heart, and that the specific influence of sodium, ammonium, potassium, 

 and magnesium on the heart's activity is similar or the same in Limulus 

 and in the vertebrates. In Linndus the heart muscle is stimulated by 

 sodium and depressed by magnesium, potassium, and calcium, as in 

 Cassiopea. 



In an interesting paper Mathews, 1907 (American Journal Physiol., 

 vol. 19, pp. 5-13), finds that MgS04 depresses the heart action of all 

 vertebrates, decreasing both amplitude and rate, but this effect is offset 

 by CaClj, as is also the case in invertebrates. 



We may conclude that while we can not prove that ionic sodium 

 produces the nervous stimulus which results in muscular activity in 

 invertebrates, we may logically entertain the suspicion that this is the 



' Mines, 1908 (Journal Physiol., Cambridge, vol. 37, pp. 408-444), finds that 

 sodium, calcium, and potassium act upon pulsating skeletal muscles of vertebrates 

 as described above for Limulus, Cassiopea, Lepas, and Annelids. 



2 Bethe, 1908 and 1909, Pfluger's Archiv fur ges. Physiol., Bd. 124, pp. 541- 

 577; Bd. 127, pp. 219-273. 



' Papers from the Tortugas Laboratory of the Carnegie Institution of Wash- 

 ington, vol. I, pp. 1 1 5-13 1, 1908. 



