ALBUMINOUS MATTERS. 93 



those which are introduced with the food. A large part of the albu- 

 minous matters of the food are derived from vegetables, and, though 

 closely related to the corresponding animal substances, are not pre- 

 cisely identical with them. Even the animal albuminous matters used 

 for food, as the albumen of eggs, the caseine of milk, and the sub- 

 stance of muscular flesh, are usually taken in the coagulated form, and 

 suffer still further changes before they become converted into the albu- 

 men of the blood. From their subsequent metamorphoses in the act 

 of nutrition they are transformed into the many specific varieties of 

 albuminous matter peculiar to the different tissues and fluids. 



Only a very small proportion of these substances is discharged with 

 the excretions. The albuminous ingredients of the perspiration and 

 sebaceous matter, and the mucus of the urinary bladder and large intes- 

 tine are almost the only ones which find an exit from the body in this 

 way. A minute quantity of albuminous matter is exhaled in a vola- 

 tile form with the breath, and a little also, in all probability, from the 

 cutaneous surface. But the entire quantity so discharged bears an 

 insignificant proportion to that which is daily introduced with the food. 

 The albuminous substances, accordingly, are decomposed in the interior 

 of the body. They are transformed by the process of destructive assi- 

 milation, and their elements are finally eliminated and discharged under 

 other forms of combination. 



