ALBUMINOSE. 87 



The white of the fowl's egg is mainly composed of a substance also 

 called albumen, and which corresponds with the albumen of blood 

 in its coagulability by heat, nitric acid, alcohol, and the metallic salts. 

 It is distinguished from the preceding mainly by its coagulability by 

 ether, which has no effect on the albumen of blood. It rotates the 

 plane of polarization to the left 35.5. 



The fresh juices of nearly all vegetables, and especially the succulent 

 plants, contain a substance coagulable by heat, which has been called 

 vegetable albumen. It may also be obtained from the cereal grains by 

 extraction with water, and resembles in its principal chemical reactions 

 the albumen derived from animal sources. 



Albuminose. 



This substance is closely related to albumen by its chemical composi- 

 tion and its general characters. It is not coagulated, however, by either 

 heat, nitric acid, or acidulated potassium ferrocyanide, but only by the 

 metallic salts and alcohol in excess. It is also distinguished by its 

 ready diffusibility through animal membranes or parchment paper ; while 

 albumen, and all other liquid albuminous matters, pass through these 

 membranes either not at all or only with great difficulty. Coagulated 

 albumen and all other digestible albuminous matters are converted 

 into albuminose by the action of gastric juice. They thus become 

 liquefied and incapable of coagulation by heat. Owing to the origin of 

 these products from the digestive act they are designated by several 

 writers under the name of peptones; and a variety of them are enume- 

 rated, but their distinctive' characters are not very sharply denned. 

 Albuminose is found in the fluids of the stomach and small intestine 

 during digestion, and exists also in the blood in the proportion of two 

 to three parts per thousand. 



Albuminose in solution has the property of modifying certain well- 

 known chemical reactions. It interferes especially with the reduction 

 of the copper oxide in Trommer's test. If a small quantity of glucose 

 be dissolved in gastric juice containing albuminose, and Trommer's test 

 applied, no peculiarity is observed on first dropping in the copper 

 sulphate ; but on the addition of potassium hydrate, the mixture takes 

 a rich purple hue, instead of the clear blue tinge which is presented 

 under ordinary circumstances. On boiling, the color changes to claret, 

 cherry red, and finally to a light yellow ; but no copper oxide is 

 deposited, and the fluid remains clear. If albuminose be present only 

 in small quantity, an incomplete reduction of the copper takes place, 

 so that the mixture becomes opaline and cloudy, but still without any 

 well marked deposit. This interference will take place when sugar is 

 present in very large proportion. We have found that gastric juice, 

 drawn from the dog's stomach during digestion, may sometimes be 

 mixed with an equal volume of honey without giving any deposit of 

 copper on the application of Trommer's test. If such a mixture, how- 

 ever, be previously diluted with water, it will often fail to prevent the 



