ALBUMENOID SUBSTANCES. 



91 



oid element of milk. There are many different kinds of these sub- 

 stances in the solid parts and secretions of the adult body, but not one 

 of them is contained under its own form in the blood, from which all 

 the nutritious material for the tissues and glands is supplied. It is 

 evident that the albumenoid substances finally present in the animal 

 frame are produced by transformation from those contained in the food 

 and in the blood. 



Only a very small proportion of the albumenoid substances is dis- 

 charged with the excretions. Those contained in the perspiration, the 

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

 intestine are almost the only ones which find an exit in this way. A 

 very little albumenoid matter is exhaled in a volatile form with the 

 breath, and a little also, in all probability, from the skin. But the entire 

 quantity so discharged bears an insignificant proportion to that intro- 

 duced with the food. The albumenoid substances, accordingly, are 

 decomposed in the interior of the body. After being produced by 

 metamorphosis in the act of nutrition, they are still further trans- 

 formed in the process of destructive assimilation, and they are repre- 

 sented, in the excreted products, by other combinations of a different 

 form. 



