502 



SCIENCE 



[N. S. Vol. XLIII. No. 1110 



omers whose work laid the foundations for 

 modern progress. 



The amateur will thus find not only clear 

 and complete directions for work, but the 

 basic principles which enable him to under- 

 stand the significance of his results. The 

 professional astronomer will also find the book 

 useful on account of its convenient collection 

 of data for which he had been obliged pre- 

 viously to search through periodicals. 



The specialist in astrophysics will naturally 

 find some points capable of clearer statement, 

 and some minor errors such as are apt to creep 

 into first editions. For example, the ZoUner 

 photometer is described on page 118 as used 

 with the historic petroleum lamp, rather than 

 with the modern incandescent lamp. The 

 lack of wave-lengths on the margins of the 

 engravings of spectra is puzzling to one not 

 thoroughly familiar with them, especially as 

 Plate XI. is printed with the violet end to the 

 right, instead of the usual direction. Chap- 

 ter XH., entitled " Eclipsing Binaries," in- 

 cludes also the " Cepheid Type," though it is 

 not claimed that their changes can be ex- 

 plained by eclipses. On page 229 is the state- 

 ment that "It was only with the selenium 

 cell that it was possible to determine a change 

 so small as 0.06 magnitude," though as a fact, 

 the extra-focal photographs are capable of de- 

 termining such changes. The use of mg. as 

 an abbreviation for magnitude, is unfortunate, 

 as it usually stands for milligram. Compare 

 the statement in the Scientific American that 

 the planet Saturn is 16 inches in diameter, 

 due to the use of the double stroke as a sign of 

 both inches and seconds of arc. This is not 

 the place to give a list of typographical 

 errors, but the statement at the top of page 

 102, that if star A is twice as bright as star 

 B, the difference in magnitude is 0.44, might 

 mislead. In the examples of the use of Pog- 

 son's rule, in Chapter Y., the omission of the 

 problem of finding the combined magnitude 

 of two or more stars, is worth mentioning. 

 In the historical part, the failure to give Mrs. 

 Fleming credit for her part in the creation of 

 the Harvard classification of stellar spectra; 

 also the failure to credit the astronomer royal, 



Christie, for the " square-root " formula for 

 the reduction of the diameters of stellar 

 images on photographs, to magnitudes, are 

 minor points which might be corrected. 



In spite of these minor criticisms the book 

 is a worthy contribution to the series cele- 

 brating the semi-centennial of Vassar College. 



J. A. Parkhuest 



Terkes Obsekvatoet, 

 Williams Bat, Wis. 



THE VITAL EQUILIBRIUM 



Following the suggestion of Nemst^ that 

 varying degrees of permeability of the plasma 

 membrane might be due to a selective solubility 

 of certain of its components, Overton estab- 

 lished his lipoid theory. The most serious 

 objection to Overton's theory is that, whereas 

 it accounts most satisfactorily for the per- 

 meability of the cell for substances which 

 normally play no part in the cell metabolism, 

 it entirely fails to explain the penetration of 

 sugars, salts and amino-acids, which must 

 constitute an essential part of the cell income. 

 Loeb^ long ago emphasized the importance of 

 the state of aggregation of the surface col- 

 loids as one factor influencing the conditions 

 of permeability. This suggestion was made 

 in connection with his experiments upon the 

 effects of pure solutions of NaCl and combina- 

 tions of ISTaCl and polyvalent ions on the eggs 

 of Fundulus. Subsequent experiments by 

 Loeb, Hober, Lillie and a host of others, have 

 established beyond a doubt the existence of a 

 physical-chemical relation between the state 

 of aggregation of the cell colloids and the 

 permeability of the cell. A precise and uni- 

 versal statement of the exact nature of this 

 relation has never been made. In the follow- 

 ing paper we shall attempt an analysis of the 

 conditions determining the viscosity of cell 

 surfaces and their importance; (1") in pro- 

 ducing changes in permeability and (2) in 

 " antagonisms." It appears that the metabolic 



iNernst, W., 

 6, 37. 



2 Loeb, J., '01, Pfliigers Arch., 

 Amer. Jour, of Physiol., 6, 411. 



, Zeitschr. f. physilcal. Chem., 

 )8; '02, 



