OCTOBEB U, 1910] 



SCIENCE 



497 



ment of special service in rapid changes of 

 surface tension. 



Loew has pointed out that potassium in 

 the condensation processes of the synthesis 

 of organic compounds has a catalytic value 

 different from that of sodium. For ex- 

 ample, ethyl aldehyde is condensed with 

 potassium salts to aldol, with sodium salts 

 to erotonic aldehyde (Kopf and Michael). 

 Potassium is, but sodium is not, effective in 

 the condensation of carbon monoxide. 

 When phenol is fused with potassium salts 

 condensation products like diphenol are 

 produced, but when sodium salts are used 

 the products are dioxybenzol and phloro- 

 glucin (Barth). It is, therefore, not im- 

 probable that potassium, along with those 

 properties which come from its ionic mo- 

 bility, has a special value in the metabolism 

 of the dim bands of striated muscle fiber 

 and in the condensation synthesis which 

 characterizes the ehromatophors of Proto- 

 phyta {Spifogyra, Zygnema) . 



"With the use of this method of deter- 

 mining differences in surface tension in 

 cells it is possible, in some cases at least, 

 to ascertain whether this force plays a part 

 in both secretion and excretion, and evi- 

 dence in favor of this view can be found in 

 the pancreatic cells of the rabbit, guinea- 

 pig, and in the renal cells of the frog. In 

 the pancreatic cells there is an extraor- 

 dinary condensation of potassium salts in 

 the ej'toplasm of each cell adjacent to the 

 lumen of the tubule, and during all the 

 phases of activity — except, it would ap- 

 pear, that of the so-called "resting-stage" 

 — potassium salts occur in, and are wholly 

 confined to, this part of each cell. It is 

 difficult to say whether they pass into the 

 lumen with the secretion and their place 

 taken by more from the blood-stream and 

 lymph, but the important point is that the 

 condensation of potassium salts immedi- 

 ately adjacent to the lumen seems to indi- 



cate a lessened surface tension on the lumen 

 surface of the cell. 



According to Stoklasa^ the pancreas of 

 the pig is much richer in potassium than in 

 sodium, the dried material containing 2.09 

 per cent, of potassium and 0.28 per cent, of 

 sodium, while the values for the dried ma- 

 terial of ox muscle are, as he determined 

 them, 1.82 and 0.26 per cent., respectively. 

 It is significant that in the pancreas this 

 large amount of potassium should be local- 

 ized as described. 



In the renal cells of vertebrates there is 

 usually a considerable amount of potassium 

 salts distributed throughout the cytoplasm. 

 These cells are always active in the elim- 

 ination of the element from the blood, and 

 it is in consequence not possible to deter- 

 mine whether there are differences in sur- 

 face tension in them. Under certain con- 

 ditions, however, these can be demon- 

 strated. In the frogs which have been kept 

 in the laboratory tanks throughout the win- 

 ter, and in the blood of which the inorganic 

 salts have been, because of the long period 

 of inanition, reduced to almost hypotonic 

 proportions, the renal cells are very largely 

 free from potassium. When it is present 

 it is usually diffused throughout the cyto- 

 plasm. If now a few cubic centimeters of 

 a decinormal solution of potassium chloride 

 be injected into the dorsal IjTuph sacs of 

 one of these frogs, and after twenty min- 

 utes the animal is killed, appropriate treat- 

 ment, with the cobalt reagent, of a thin 

 section of the fresh kidney made by the 

 carbon dioxide freezing method, reveals in 

 the ceUs of certain of the tubules a con- 

 densation of potassium salts in the cyto- 

 plasm immediatelj' adjacent to the wall of 

 the lumen. There is also a very slight 

 diffuse reaction throughout the remainder 

 of the cytoplasm, except in that part imme- 

 diately adjacent to the external boundary 



' Stoklasa gave the values in K,0 and NajO. 



