124 HUMAN PHYSIOLOGY. 



the joints where the movement takes place, and when the muscles 

 are considered as sources of power for imparting movement to the 

 levers, with the object of overcoming resistance or raising weights. 



In mechanics, levers of three kinds or orders are recognized, ac- 

 cording to the relative position of the fulcrum or axis of motion, the 

 applied power, and the weight to be moved. (See Fig. 5.) 

 2. Red and white corpuscles, these constituting by weight less than 



one half (40 per cent.) of the entire amount of blood. 



COMPOSITION OF PLASMA. 



Dalton, 



Water 902.00 



Albumin 53*oo 



Paraglobulin 22.00 



Fibrinogen 3.00 



Fatty matters 2.50 



Crystallizable nitrogenous matters 4.00 



Other organic matter . 5.00 



Mineral salts 8.50 



1,000.00 



Water acts as a solvent for the inorganic matters and holds in 

 suspension the corpuscular elements. 



Albumin is the nutritive principle of the blood ; it is absorbed by 

 the tissues to repair their waste and is transformed into the organic 

 basis characteristic of each structure. 



Paraglobulin or fibrinoplastin is a soft, amorphous substance pre- 

 cipitated by sodium chlorid in excess, or by passing a stream of car- 

 bonic acid through dilute serum. 



Fibrinogen also can be obtained by strongly diluting the serum and 

 passing carbonic acid through it for a long time, when it is precipi- 

 tated as a viscous deposit. 



Fatty matter exists in the blood to the extent of about 0.25 per 

 cent. Just after a meal rich in fat, this amount may be considerably 

 increased. Within a few hours it disappears, though its ultimate 

 fate is unknown. 



Sugar is represented by dextrose. The amount present varies 

 from o.i to 0.3 per cent. It is derived directly from the glycogen of 

 the liver. Should the normal percentage be increased, the sugar 

 is eliminated by the kidneys. 



