308 PHYSIOLOGY AT THE FARM. 



Proteine. Though Liebig refuses to adopt the ideas of 

 Mulder on the subject of proteine namely, that albumen, 

 fibrine, and caseine are derivations of one fundamental azotised 

 principle, and that this substance, by its union with different pro- 

 portions of sulphur and of phosphorus, gives rise to these three 

 modifications of the albuminoid group yet the following pas- 

 sage will show how closely, in his opinion, these three nutritive 

 principles are allied : " These nitrogenised forms of nutriment 

 in the vegetable kingdom may be reduced to three substances, 

 which are easily distinguished by their external characters. 



"When the newly-expressed juices of vegetables are allowed 

 to stand, a separation takes place in a few minutes. A gelati- 

 nous precipitate, commonly of a green tinge, is deposited, and 

 this, when acted on by liquids which remove the colouring mat- 

 ter, leaves a greyish-white substance, well known to druggists as 

 the deposit from vegetable juices. The juice of grasses is espe- 

 cially rich in this constituent, but it is most abundant in the 

 seeds of wheat and of the cerealia generally. It may be obtained 

 from wheat-flour by a mechanical operation and in a state of to- 

 lerable purity ; it is then called gluten, but the glutinous property 

 belongs in part to an oily substance present in small quantity. 



" The second nitrogenised compound remains dissolved in the 

 juice after the separation of the fibrine. It does not separate 

 from the juice at the ordinary temperature, but is instantly coagu- 

 lated when the liquid containing it is heated to the boiling point. 



"When the clarified juice of nutritious vegetables, such as 

 cauliflower, asparagus, mangel-wurzel, or turnips, is made to 

 boil, a coagulum is formed, which it is absolutely impossible 

 to distinguish from the substance which separates as a coagu- 

 lum when the serum of blood, or the white of an egg diluted 

 with water, is heated to the boiling point. 



" The third of these important vegetable principles is chiefly 

 found in the seeds of peas, beans, lentils, and similar legumi- 



