ELECTRICAL AND MAGNETIC PROPERTIES OF THE CELL 47 



Faraday's contradictory observations are not quite so easily disposed 

 of, and hence it seemed of interest to repeat and extend or overthrow the 

 somewhat scanty observations made by him upon plant and animal sub- 

 stances. It may at once be mentioned that all external contamination with 

 iron was avoided throughout. The magnetic permeability of a compound 

 material is naturally the algebraic sum of the magnetic permeabilities of 

 the separate constituents, multiplied by the fractional amounts of them 

 present. An estimate of the magnetic permeability of a substance can best 

 be made by noting the directive action of a magnetic field upon it when 

 suspended in liquids of known permeability. Air is very feebly diamagnetic, 

 and hence a body, which is paramagnetic in air, will usually be para- 

 magnetic in a vacuum also ; alcohol is, however, much more strongly 

 diamagnetic than air, and water still more so. The following table gives 

 the results obtained in these media : 



1 Solids were cut or cast into short rods ; liquids or solids acted on by the medium were placed 

 in thin, very feebly paramagnetic glass tubes. 



* Blood contains barely 0-2 per cent, of fibrin, and nearly twice as much haemoglobin (13-5 per 

 cent.) as albumin 7-6 per cent., the fats, salts, and extractives totalling less than I per cent. 



s I have since found that the same result has been obtained by Gamgee (Proc. Royal Soc., 1901, 

 Vol. LXVIII, p. 503) in the case of both oxyhaemoglobin and CO-haemoglobin. 



