NON-NITROGENIZED CONSTITUENTS OF THE BODY. 439 



and the capacity for muscular work and endurance. The nutritive activity 

 of other parts and organs is limited and is not sensibly affected by an excess 

 of nitrogenized food. 



In addition to the albuminoids of the blood, lymph, chyle and secreted 

 fluids, and those which have been described as alimentary matters, the fol- 

 lowing have been found in various tissues and organs of the body. 



Cystalline, a nitrogenized substance in the crystalline lens. 



Myosine, a substance extracted from muscular tissue, of which it is the 

 chief nitrogenized constituent. 



Keratine, found in the epidermis and its appendages. 



Elastine, the nitrogenized constituent of the elastic tissues. 



Osseine, in bones, and chondrine, in cartilage. 



Gelatine, probably not a normal constituent of the body, but a substance 

 formed from the connective tissues by prolonged boiling in water. 



Certain nitrogenized substances containing phosphorus, found in the 

 nervous tissues, which will be described in connection with the chemistry of 

 the nervous system. 



The changes involved in nutrition, assimilation, or nutritive metabolism, 

 are apparently dependent upon properties belonging to the nitrogenized con- 

 stituents of the tissues. When the supply of new matter is equal to the de- 

 structive metabolism, the system is in what is called a condition of equilib- 

 rium, and the body neither gains nor loses in weight. In growth, the supply 

 exceeds the waste, and in the opposite condition, the waste exceeds the supply. 



Certain liquids and tissues of the human body may be restored after 

 their destruction. The blood and its corpuscles undergo regeneration. Blood- 

 vessels, also, may be regenerated, being developed first as capillaries and 

 afterward as arteries and veins. The same is probably true of lymphatics. 

 The epidermis and its appendages and certain parts of the true skin may be 

 regenerated after destruction. Muscular substance, after certain kinds of 

 degeneration in disease, as in fevers, may be restored. Portions of nerves 

 may be regenerated after division or exsection. A divided tendon may become 

 reunited by connective tissue. Portions of cartilage or bone may be regen- 

 erated, if the perichondrium or the periosteum remain intact. When wounded 

 or lost parts are not absolutely restored, the divided tissue is reunited or the 

 lost tissue is supplied by what is called cicatricial connective tissue. 



Non- Nitrogenized Constituents of the Body. Under the head of alimen- 

 tation, the general properties of non-nitrogenized matters (starch, sugars 

 and fats) have been fully described. These are important constituents of 

 food, but in themselves they are incapable of supporting life. They are 

 introduced as food, but are destroyed in the organism and are never dis- 

 charged from the body in health in the form in which they entered. 



The carbohydrates (starch and sugars) are all converted into glucose in di- 

 gestion. As glucose they are taken up by the blood and carried to the liver, 

 where they are in great part and probably entirely converted into glycogen. 

 The glycogen thus formed is stored up in the liver and is gradually transformed 

 into animal sugar, which passes into the blood slowly and gradually, and 



