June 7, 1918] 



SCIENCE 



569 



inert chemical substances, such as the passage 

 of sugars through the intestines or of urea 

 through the kidney. But no decided changes 

 in tlie molecules seem necessary. The condi- 

 tions in the membrane cells may be favorable 

 for weakly combined synthetic derivatives 

 with the right solubilities. A\Tien we realize 

 how susceptible to small differences in salts 

 the membranes are, it is not impossible that 

 some particular salt of the passing substance 

 may be all that is necessary to determine its 

 ready exit. If all other ideas fail in any given 

 case, one can always fall back on the ever- 

 ready help of the all-pervasive enzyme. 



Several other writers have stated that these 

 selective membranes behave as though a genie 

 stood at the opening in the membrane, allow- 

 ing the molecules from the side of lower con- 

 centration to pass, while closing the door to 

 those moving in the opposite direction. It is 

 evident that a space in which the proper chem- 

 ical reaction occurs, and which is situated be- 

 tween the two different membranes with the 

 proper permeabilities, functions like our an- 

 thropomorphic genie. 



It is rather apparent that the idea outlined 

 above is about half way between that of or- 

 dinary permeability and secretion. Though 

 it does have many points in common with se- 

 cretion, it seems wise not to confuse the two; 

 for it is clear that they are different in the 

 purpose served as well as in the method of 

 obtaining their results. 



If the attention is confined to the isolated 

 system, solution one, the cell membrane as a 

 whole, and solution two with concentration 

 greater than solution one, the law of the con- 

 servation of energy is not obeyed. This might 

 be urged as evidence of vitalism. But closer 

 scrutiny will show that the necessary energy 

 to run this system comes from outside. The 

 substance necessary for the chemical reaction 

 has to be formed and sent to the proper place. 

 If this substance is derived from solution two 

 directl.y, energy equivalent to that produced 

 in the combination must be supplied to dis- 

 sociate the complex. And energy is necessary 

 to transport this substance back again to the 

 permeability cell. Energy is also consumed in 



maintaining the cell structure. Even in a 

 living organism one hesitates to start a per- 

 petual motion theory, partly because it is such 

 a lazy way of settling a difficulty, and partly 

 because it would necessitate a later disillu- 

 sionment. C. G. MacArthur 

 Medical School, 



Stanford Univeesitt 



THE AMERICAN ASSOCIATION FOR 



THE ADVANCEMENT OF SCIENCE 

 SECTION B 



The section convened at Pittsburgh at 10 a.m., 

 December 27, 1917, in Room 209 of the School of 

 Applied Science, Carnegie Institute of Technology. 

 Its sessions, jointly with those of the American 

 Physical Society, extended over a period of three 

 days. The scientific papers presented under the 

 auspices of the American Physical Society are as 

 follows : 



' ' The optical properties of ruhidium, " by J. B. 

 Nathanson, Carnegie Institute of Technology. 



"A preliminary study of the luminescence of the 

 uranyl salts under cathode ray excitation," by 

 Frances G. Wick, Vassar College, and Louise S. Mc- 

 Dowell, Wellesley College. 



"Note on a phosphorescent calcite," by E. L. 

 Nichols and H. L. Howes, Cornell University. 



"The visibility of radiation in the blue end of 

 the visible spectrum," by L. W. Hartmau, Univer- 

 sity of Nevada (communicated from the Nela Ee- 

 search Laboratory, Cleveland). 



"An improved form of mercury vapor air 

 pump," by Chas. T. Knipp, University of Illinois. 



"Heat condwtivity of cerium," by C. N. Wen- 

 rich and G. G. Becknell, University of Pittsburgh. 



' ' Temperature and heat of fusion, " by J. E. 

 Siebel, Chicago. 



" Eeport on the constructio7i of certain mathe- 

 matical tables," by C. E. Van Orstrand, U. 8. 

 Geological Survey, Washington, D. C. 



"Mobilities of ions in vapors," by Kia-Lok Yen, 

 University of Chicago. 



' ' The size and shape of the electron, ' ' by Arthur 

 H. Compton, Westinghouse Lamp Company. 



"The coefficient of emission and absorption of 

 photo-electrons from platinum and silver," by 

 Otto Stuhlmann, Jr., University of Pennsylvania. 



"Ionization and excitation of radiation by elec- 

 tron impact in nitrogen," by Bergen Davis and 

 P. S. Goucher, Columbia University. 



"Energy in continuous X-rny spectra," by C. T. 

 Llrey, Columbia University. 



