EFFECTS OF POTASSIUM. 43 



the activity of the marginal sense-organs sooner than it affects the 

 disk itself. The disk without sense-organs will, however, cease to pul- 

 sate in a solution resembling sea -water but lacking potassium quite 

 as quickly as will the perfect Medusa. It would seem, therefore, that 

 the sense-organs and the sensory surface of the sub-umbrella are 

 equally intolerant of a lack of potassium in the sea- water. This is 

 interesting in view of the fact that the disk without sense-organs is 

 relatively indifferent to calcium, or magnesium, and will pulsate either 

 in sea- water saturated with CaSO 4 , in normal sea- water, or for more 

 than an hour in a solution resembling sea- water but without calcium. 

 The Medusa with sense-organs intact, however, ceases to pulsate in 

 a solution containing all of the elements of sea-water excepting cal- 

 cium in less than six minutes, but will pulsate in sea- water satu- 

 rated with CaSO 4 . It is evident that the accurate balance between the 

 proportions of calcium, potassium, and sodium insisted upon by L,oeb 

 as being necessary for the continuance of pulsation need not be main- 

 tained and yet pulsation may continue. As Howell has pointed out, 

 marine animals are attuned to the sea- water in which they live, and 

 any change in its constituents must be expected to affect them more 

 or less adversely. Loeb's theory of the influence of ions upon pulsa- 

 tion, although of fundamental value, unfortunately neglects, in some 

 measure, to consider the effects of the salts as a whole. As we shall 

 soon see, however, Cassiopea will pulsate for at least 30 minutes in a 

 pure ^n NaCl solution, whereas it is paralyzed in less than a minute 

 in an isotonic solution of Na 2 CO 3 . Indeed, the various potassium 

 salts stimulate in different degrees. KI, K 2 SO 4 , and KC1 are powerful 

 stimulants, whereas KMnO 4 , KA1(SO 4 ) 2 , and potassium metabisulphite 

 produce weak contractions. 



Matthews (1905) concludes that valence, as such, either of the anion 

 or cation, is of secondary or no importance in determining either the 

 toxic or antitoxic action of the salt. 



L,oeb (1900) concluded that the potassium and calcium ions of sea- 

 water prevent the center of the bell of Gonionemus from pulsating 

 rhythmically. His experiment, however, does not prove this point, 

 for he found that the center of the bell of Gonionemus would pulsate 

 in ^n NaCl, but not in sea- water ; and thus he concluded that the K 

 and Ca of sea-water inhibited pulsation,* but he neglected to consider 



*While this paper was in press Loeb (1906 : Journ. Biol. Chemistry, vol. i, p. 431) 

 concludes that magnesium and calcium inhibit the center of Gonionemus. In so far 

 as the effect of magnesium is concerned his view now accords with the researches of 

 Tullberg (1892), Meltzer and Auer (1905-06), and Mayer (1906) that magnesium is 

 anesthetic or inhibitory. 



