206 



SCIENCE. 



[N. S. Vol. IX. No. 215. 



the Alaskan investigation. The value of 

 additions to equipment of the stations in 

 1898 is estimated as follows: Buildings, 

 $109,851.65; libraries, $11,700.73; appa- 

 ratus, $19,195.43 ; farm implements, $10,- 

 800.27; live stock, $13,151.33; miscel- 

 laneous, $11,972.97 ; total, $176,469.41. 



The stations employ 669 persons in the 

 ■work of administration and inquiry. The 

 number of ofiBcers engaged in the different 

 lines of work is as follows : Directors, 75 ; 

 chemists, 148 ; agriculturists, 71 ; experts 

 in animal husbandry, 10 ; horticulturists, 

 77 ; farm foremen, 29 ; dairymen, 21 ; bot- 

 anists, 50 ; entomologists, 46 ; veterina- 

 rians, 26; meteorologists, 20 ; biologists, 11 ; 

 physicists, 11; geologists, 6; mycologists 

 and bacteriologists, 19 ; irrigation engi- 

 neers, 7 ; in charge of substations, 15 ; sec- 

 retaries and treasurers, 23 ; librarians, 10, 

 and clerks, 46. There are also 21 persons 

 classified under the head of " miscellan- 

 eous," including superintendents of gardens, 

 grounds and buildings, apiarists, herdsmen, 

 etc. Three hundred and five station officers 

 do more or less teaching in the colleges with 

 which the stations are connected. 



During 1898 the stations published 406 

 annual reports and bulletins. Besides reg- 

 ular reports and bulletins, a number of the 

 stations issued press bulletins, which were 

 widely reproduced in the agricultural and 

 county papers. The mailing lists of the 

 stations now aggregate half a million 

 names. Correspondence with farmers 

 steadily increases, and calls upon station 

 ofiBcers for public addresses at institutes 

 and other meetings of farmers are more 

 numerous each year. The station officers 

 continue to contribute many articles on 

 special topics to agricultural and scientific 

 journals. A number of books on agricul- 

 tural subjects, written by station officers, 

 have been published during the past year. 

 A. C. True. 



U. S. Department of Agriculture. 



PHYSIOLOGICAL OSMOSIS. 



In going over this subject I have discov- 

 ered a verjr simple method, which I would 

 offer as an improvement on that of van't 

 Hoff, referred to, and its results given by 

 Starling in Schaefer's ' Physiology.' 



All methods as to osmotic pressure are 

 an application of the discovery that it is 

 the largeness or smallness of the chemical 

 molecules of solutes (matters in solution) 

 that determines whether they shall be 

 estopped by or shall pass through mem- 

 branes. Citing common-places of chemis- 

 try, we know that a gram- molecule of 

 hydrogen gas, with a numerical value of 2, 

 has the same volume as a gram-molecule of 

 oxygen, weighing 32 per molecule, and as a 

 gram-molecule of cane sugar dissolved in 

 water, having a molecular weight of 342 and 

 when in solution acting like a gas. The 

 common volume of a gram-molecule of 

 each of these substances, at 0°C. and ordi- 

 nary barometric pressure, is 22.32 liters ; 

 if the gases be compressed to the volume 

 of 1 liter they will exercise a pressure of 



22.32 atmospheres per gram-molecule. This 

 is the result with all solutions in water 

 when taken according to their molecular 

 pressure. But it will not apply to electro- 

 lytes, as these are broken up by the water ; 

 thus for sodium chlorid the value is 1.6 

 times this amount. 



Taking as an example a 1 per cent, solu- 

 tion of cane-sugar in water, a gram-mole- 

 cule, that is 342 gi-ams, of the sugar are 

 dissolved in 34,200 grams of water, or 

 \-f-o: of a gram-molecule in a liter of water. 

 This will, therefore, exert -Jgf"^ of 22.32 

 atmospheres of pressure ; or taking 10.33 

 meters of water pressure for an atmos- 

 phere, we find from the osmotic pressure 

 of the solution at 0°C. p = ^W X 22.32 x 



10.33 = 6.748 meters of water-pressure. 

 At the ordinary temperature of the body, 



37°C., this will be increased by -^i^ of 



