August 20, 1909] 



SCIENCE 



247 



again supports the view that permeability is 

 temporarily increased during stimulation. 



5. A close inorganic parallel to certain 

 characteristic phenomena of stimulation is 

 seen in the pulsating mercury hydrogen per- 

 oxide catalysis of Bredig and his collabora- 

 tors. The electrical rhythm accompanying 

 the rhythm of oxygen-evolution has been 

 shown by Antropoff to run parallel with the 

 formation and dissolution of a surface-film of 

 mercury peroxidate. Here we have apparently 

 an actual instance of a rhythmical change of 

 potential which is due to rhythmical altera- 

 tion of a surface-film ; the marked resemblance 

 in time-relations and in other respects to 

 many rhythmical processes in organisms sup- 

 ports the view that a similar surface-change is 

 the basis of the electrical variations accom- 

 panying automatic rhythmical stimulation in 

 living tissues. The alternate formation and 

 dissolution of the film over the mercury 

 surface would correspond respectively to the 

 alternate decrease and increase of permeabil- 

 ity in the living cells. 



The following special observations and ex- 

 periments, made chiefly during the past sum- 

 mer at Woods Hole, furnish, it is believed, 

 strong confirmatory evidence of the truth of 

 the above general view. The organisms used 

 were the larvaj of the annelid Arenicola cris- 

 iata, which are readily obtainable in large 

 quantity at Woods Hole. These are bi- 

 trochal larvte ca. 0.3 millimeters in length, 

 with three setigerous body-segments; they 

 swim actively by their cilia, showing pro- 

 nounced positive phototaxis, and have a well- 

 developed muscular system ; and the cells are 

 remarkable for containing large quantities of 

 a water-soluble yellow pigment. This sub- 

 stance serves as an index of inerea.sed perme- 

 ability by diffusing at such times from the cells 

 and coloring the medium; such loss of pig- 

 ment occurs during intense stimulation, after 

 death, or under the influence of cytolytic sub- 

 stance.? (chloroform, etc.), but not during the 

 normal activities of the animal; the phenom- 

 enon indicates therefore an abnormally great 

 increase of permeability. 



When Arenicola larvae are transferred 

 from sea-water into pure isotonic solutions of 



various alkali and alkali-earth salts (e. g., 

 NaCl, KCl, NH.Cl, LiCl, CsCl, RbCl, SrCl,, 

 BaCl.) they contract strongly to almost half 

 the normal length and remain contracted for 

 several seconds. During this interval the yel- 

 low pigment diffuses freely from the cells and 

 colors the solution. Isotonic CaClj and 

 MgCL, on the other hand, have no such in- 

 tense stimulating action and cause no loss of 

 pigment; in these solutions the larvae remain 

 straight and extended and muscular move- 

 ments cease (anesthethic action). Addition 

 of a little CaCL (1 volume m/2 CaCL to 24 

 volumes m/2 NaCl) to isotonic NaCl solution 

 prevents the initial stimulating action of the 

 pure salt and at the same time the loss of 

 pigment; in this mixed solution larvse remain 

 living and active for greatly prolonged 

 periods (antitoxic action of Ca ions). Both 

 the stimulating action and the toxicity of the 

 pure sodium salt are thus associated with a 

 marked increase of permeability; if this last 

 is checked, as by the presence of appropriate 

 bivalent cations (Ca, Mg, etc.), the two 

 former effects also disappear. Solutions of 

 MgCl, and similarly acting salts and anes- 

 thetics appear, on the contrary, to decrease 

 the normal permeability. Stimulation is thus 

 associated with an increase and inhibition 

 with a decrease of permeability. 



The electrolytes affect permeability presum- 

 ably by influencing the state of aggregation 

 of the colloids composing the plasma mem- 

 brane. The consistency of the latter may 

 also be changed by altering the condition of 

 its lipoid constituents. It was found that 

 relatively strong solutions of lipoid-solvents 

 in sea-water, or even in m/2MgCL solution 

 (one half to one third saturated chloroform; 

 saturated ether or benzole), also produce 

 strong muscular contractions accompanied by 

 loss of pigment. Solutions of this concen- 

 tration are rapidly destructive to the larvae; 

 in lower concentrations the lipoid-solvents 

 have the opposite action, cheeking activity 

 (anesthetic action) without stimulation or 

 loss of pigment. In general, the lipoid-sol- 

 vents in low concentration appear to decrease 

 permeability and hence temporarily to s^ispend 

 activity without toxic action (anesthesia) ; in 



