XIII. THE ANIMAL 265 



PERCENTAGE COMPOSITION OF THE WHOLE BODIES OF ANIMALS. 



Among the most important parts of the animal body, the following 

 may be mentioned : 



(1) The blood. 



(2) The bones. 



(3) The muscles. 



(4) The connective tissues. 



Blood consists of a transparent colourless liquid, the blood plasma, 

 in which an immense number of solid particles, the red and colourless 

 corpuscles, are suspended. When taken from the body, unless special 

 precautions are observed, blood coagulates or clots with a rapidity 

 which varies with different animals and also with the temperature ; if 

 cooled quickly, coagulation is retarded ; the blood of the horse coagu- 

 lates more slowly than that of other animals. 



In clotting, a separation into a clear yellow liquid blood serum 

 and a red solid blood clot occurs. This separation is brought about 

 by the coagulation of a proteid fibrinogen which exists in blood 

 plasma and which can be removed by beating the blood during clotting. 

 Blood serum thus differs from blood plasma in containing no fibrin- 

 ogen and a smaller quantity of calcium, magnesium and phosphoric acid. 



Blood serum is of a sticky consistency, of alkaline reaction, and 

 has a specific gravity of about 1-028. It contains fats, soaps, choles- 

 terol, C 26 H 43 OH, lecithin, C,H 4 (OH)(CH 3 ),N.HPO 4 .C 3 H 5 :(C 1S H 36 O 2 ) 2 , 

 albuminoids, glucose and traces of urea, uric acid, creatine, lactic acid 

 and hippuric acid. 



The following analyses of serum were made by Hammarsten : 



