140 THE POPULAR SCIENCE MONTHLY 



jury on the cell and eventually causing death. Loss of essential cell- 

 constituents through the altered membrane would have this effect. 

 Now there is evidence that a large class of injurious or toxic substances 

 exert their destructive action by altering the surface-films of cells and 

 permanently increasing the permeability. When this occurs in such a 

 cell as a blood-corpuscle or a sea-urchin egg — which is normally in 

 osmotic equilibrium with its medium — the cell first swells (an effect 

 showing loss of osmotic equilibrium) and eventually dissolves or dis- 

 integrates, an effect known as cytolysis. Lipoid-solvents, like chloro- 

 form or ether, have this effect in concentrations above certain minima : 

 they disrupt the membrane, presumably by altering the condition of the 

 lipoids, and disintegration follows. Many toxic alkaloids and gluco- 

 sides — like saponin, digitalin, aconitin, etc. — and certain bacterial prod- 

 ucts — cytolysins and hemolysins — have similar effects. Other sub- 

 stances, as inorganic salts, acids, or alkalis, may cause cytolysis by alter- 

 ing the state of the colloids of the membrane. In certain typical in- 

 stances there is direct evidence that the toxic action is primarily due to 

 a surface-alteration, and consists in a destruction of the semi-perme- 

 able properties of the membrane. Certain fluorescent substances like 

 eosin exert a cytolytic action on many cells in the presence of light, 

 though inactive in the dark (photodynamic action). Harzbecker and 

 Jodlbauer found that blood-corpuscles so treated began to swell before 

 there was any perceptible entrance of the dye into the cell, i. e., the 

 initial stage of cytolysis, involving a loss of osmotic equilibrium, oc- 

 curred previously to the entrance of the toxic substance. But loss of 

 osmotic equilibrium, unless soon reversed, involves destruction of the 

 cell. The essential or critical toxic action in this case is thus super- 

 ficial, and what is true of eosin is probably true of many other — 

 possibly most — cytolytic substances. 



The peculiar antagonisms existing between the physiological ac- 

 tions of various substances (e. g., muscarin and atropin, toxin and 

 antitoxin, etc.) are probably in many cases to be explained on this 

 basis. The toxic and antitoxic actions of neutral salts form a case in 

 point. Pure solutions of sodium salts, even sodium chloride, are 

 strongly toxic to many cells, particularly those of marine organisms, as 

 the work of J. Loeb and his successors has shown with especial clear- 

 ness ; but if to the pure solution a little calcium salt is added, this toxic 

 action is prevented or greatly diminished; the calcium (or other favor- 

 able salt) counteracts the toxic action of the sodium salt — in other 

 words, has an antitoxic action. Now it can readily be shown in certain 

 organisms that the toxic action of the pure sodium salt solution is 

 associated with a strong permeability-increasing action. As test-ob- 

 jects or physiological indicators in the investigation of these effects I 

 have used the pigment-containing eggs of the sea-urchin, Arbacia, and 

 the larva? of a marine annelid, Arenicola, whose cells contain a water- 



