ORGANIC PRINCIPLES. 83 



the property of deviating the plane of polarization to the 

 left. He has employed a polarizing apparatus like the one 

 used by Biot in the examination for sugar, for the purpose 

 of estimating the quantity of albumen in a watery mixture, 

 and found that " each minute of deviation corresponds to 

 18 decigrammes (29*77 grains) of dried albumen in 1,000 

 cubic centimetres (1*76 pints) of water." : This instrument he 

 calls an albuminimeter. A current of galvanism passed 

 through a mixture containing albumen produces coagulation, 

 which has been attributed to a decomposition of certain salts 

 which are combined with it and maintain its fluidity. 



Some organic principles almost identical with albumen 

 in chemical reactions, are found to possess very different 

 vital properties. One of these is the organic principle of 

 the gastric juice, which, like albumen, is coagulable by 

 heat, alcohol, and the metallic salts, but exerts a peculiar 

 and distinctive action in the digestion of certain articles of 

 food. 



Tests for Albumen. As a pathological condition, albu- 

 men sometimes exists in the urine, and it becomes important 

 clinically to be able to determine this fact by the application 

 of tests. These require certain precautions for their suc- 

 cessful application. They depend upon its property of 

 coagulation. 



If a solution containing albumen be exposed to heat 

 in a test tube, as the temperature rises a slight cloudiness 

 or opacity in the upper part of the liquid occurs, which 

 gradually extends through the whole mass, until, at a 

 temperature of about 167, a precipitate more or less abun- 

 dant is produced, which is entirely insoluble. If albumen be 

 very abundant, the whole mass may become solidified, and 

 we may have all shades between this and the slight opacity 

 produced by a very minute quantity. In the latter case 



1 BECQUEREL and RODIER, Traite de Chimie Pathologique, Paris, 1854, p. 53. 



