138 ANIMAL PHYSIOLOGY. 
Na Cl is more abundant in the fluids of animals; K and 
phosphates more abundant in the tissues. 
Earthy salts are most abundant in the harder tissues. 
The salts are probably not much, if at all, changed in their 
passage through the body. 
In some cases there is a change from acid to neutral or 
alkaline. 
The salts are essential to preserve the balance of the nutri- 
tive processes. Their absence leads to disease, e. g., scurvy. 
GENERAL CHARACTERISTICS OF PROTEIDS. 
They are the chief constituents of most living tissues, in- 
cluding blood and lymph. 
The molecule consists of a great number of atoms (complex 
constitution), and is formed of the elements C, H, N,O,S, and P. 
All proteids are amorphous. 
All are non-diffusible, the peptones excepted. 
They are soluble in strong acids and alkalies, with change 
of properties or constitution. 
In general, they are coagulated by alcohol, ether, and heating. 
Coagulated proteids are soluble only in strong acids and 
alkalies. 
Classification and Distinguishing Characters of Proteids. 
1. Native albumins: Serum albumin; egg albumin; soluble 
in water. 
2. Derived albumins (albuwminates): Acid and alkali albu- 
min; casein; soluble in dilute acids and alkalies, insoluble in 
water. Not precipitated by boiling. 
3. Globulins: Globulin (globin); paraglobulin; myosin; 
fibrinogen. Soluble in dilute saline solutions, and precipitated 
by stronger saline solutions. 
4. Peptones: Soluble in water; diffusible through animal 
membranes; not precipitated by acids, alkalies, or heat. De- 
rived from the digestion (peptic, pancreatic) of all proteids. 
5. Fibrin: Insoluble in water and dilute saline solutions. 
Soluble, but not readily, in strong saline solutions and in dilute 
acids and alkalies. 
CERTAIN NON-CRYSTALLINE BODIES. 
The following bodies are allied to proteids, bit are not the 
equivalents of the latter in the food. 
