June 27, 1913] 



SCIENCE 



969 



anatomical features of the required kind. 

 It is a small, worm-like trochopliore 

 about 0.3 mm. long, swimming by two 

 ciliated rings and possessing a well- 

 developed musculature of longitudinal 

 fibers. The body cells are permeated with 

 a yellow or brownish pigment, so that 

 when the larvae are collected in a dense 

 mass (which can readily be done by taking 

 advantage of their strong heliotropism) 

 they appear dark brown in color. Now if 

 such a mass of larvte is brought suddenly 

 into a pure isotonic NaCl solution, they in- 

 stantly contract strongly and remain thus 

 contracted for twenty or thirty seconds, 

 after which they slowly relax. During the 

 period of contraction the yellow pigment 

 diffuses rapidly into the solution and colors 

 the latter bright yellow ; i. e., strong stimu- 

 lation of the muscle cells is associated with 

 marked increase in the permeability of the 

 pigment-containing ceUs. The cilia cease 

 and undergo rapid disintegration at the 

 same time. If now instead of using pure 

 NaCl solution, we bring a similar mass of 

 larvffi into NaCl solution to which a little 

 calcium or magnesium chloride has been 

 added, a strikingly different effect is seen. 

 Stimulation is slight and transitory, there 

 is no immediate loss of pigment, and ciliary 

 action continues uninterrupted. The gen- 

 eral toxic action of the NaCl is also greatly 

 lessened. It can thus be shown that pure 

 solutions of sodium salts cause strong stim- 

 ulating and permeability-increasing effects, 

 both of which are simultaneously prevented 

 by the addition of a little calcium or other 

 antitoxic salt. Prevention of permeability- 

 increase runs parallel with prevention of 

 stimulation. Magnesium salts in pure iso- 

 tonic solution exhibit an action which is 

 apparently the reverse of that shown by 

 sodium salts. Larv£e brought into m/3 

 MgCl, show no stimulation, no loss of pig- 

 ment or destruction of cilia, and little or no 



immediate injury. On the contrary all 

 muscular movements cease in a few seconds 

 and the larva3 remain permanently motion- 

 less during their stay in the solution (ex- 

 cept for the cilia which remain active). 

 The effect of the solution is reversible; on 

 return after a few minutes to sea-water, the 

 normal activities at once return. The mag- 

 nesium salt shows typical anesthetic action, 

 i. e., it renders stimulation difficult or im- 

 possible. It also hinders increase of per- 

 meability. If larva3 that have lain in m/3 

 MgCl, for a few minutes are suddenly 

 brought into m/2 NaCl, no immediate effect 

 is seen — neither stimulation nor loss of pig- 

 ment. The toxic action of the pure NaCl is 

 also much less than when the transfer to 

 this solution is made directly from sea- 

 water. In other words, the MgClj renders 

 the plasma-membranes resistant to the per- 

 meability-increasing or cytolytic action of 

 the NaCl solution; and at the same time it 

 renders the irritable elements resistant to 

 stimulation. The action of the MgCL must 

 depend on an alteration of the cell-surfaces, 

 since this salt enters living cells with ex- 

 treme slowness, if at all. We must con- 

 clude that in this instance at least the an- 

 esthetic action depends on a modification 

 of the surface-layers or plasma-membranes 

 of the irritable cells or elements. 



I have found that lipoid-solvent anesthet- 

 ics produce effects which are essentially 

 identical with those of MgCL. The ease of 

 ethyl ether, the most widely used of all an- 

 esthetics, may serve as an illustration. In a 

 .7 per cent, solution of ether in sea-water 

 Arenicola larvse immediately cease all mus- 

 cular movements; the cilia show more re- 

 sistance to anesthesia and remain active. 

 If now the larvs are transferred to m/2 

 NaCl solution containing the same propor- 

 tion of ether — so as to preserve the state of 

 anesthesia — no contraction or loss of pig- 

 ment follows, the cilia continue their activ- 



