THE PENETRATION OF CATIONS INTO LIVING CELLS. 



By matilda MOLDENHAUER BROOKS. 

 {From the Division of Pharmacology, Hygienic Laboratory, Washington, D. C.) 



(Received for publication, November 25, 1921.) 



According to some investigators the living cell is impermeable to 

 salts, while according to others it is permeable to anions but not to 

 cations. The object of the present investigation is to throw some 

 Light on the problem by making direct determinations of the pene- 

 trating substances. 



The literature of the permeability of protoplasm to salts has been 

 summarized by Brooks^ and will not be discussed here. Attention 

 may, however, be called to the fact that satisfactory direct methods 

 of study have been lacking. The importance of obtaining direct 

 evidence of the penetration of substances into the protoplasm cannot 

 be overestimated. 



The demonstration of direct penetration has been very difficult 

 because individual cells are usually so small that their contents can- 

 not be analyzed. Meyer,^ Hansen,^ Wodehouse," and Crozier,* have 

 examined the cell contents of Valonia for evidence of penetration of 

 salts from sea water. In this case the cell sap can be obtained with- 

 out contamination and in sufficient quantities for examination. 



By employing a large form of Nilella the writer was able to investi- 

 gate the penetration of several cations from balanced and from unbal- 

 anced solutions. This species of Nitella is especially favorable because 

 of the length of the (multinucleate) cells (5 inches is not unusual), and 

 the amount of cell sap which can be expressed from a single cell. 



1 Brooks, S. C, Bot. Gaz., 1917, Ixiv, 230. 



2 Meyer, A., Ber. dcutsch. bot. Gcs., 1891, ix, 79. 

 'Hansen, A., Mitt. Zool. Stat. Neapel, 1893, xi, 255. 

 * Wodehousc, R. P., /. Biol. Chem., 1917, xxix, 453. 

 5 Crozicr, W. J., J. Gen. Physiol., 1918-19, i, 581. 



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