CHEMICAL COMPOSITION OF THE BLOOD 133 



contain a nucleo-protein, and it is supposed that they take part in the phe- 

 nomenon of coagulation. According to Deetjen and others, ameboid move- 

 ment has been demonstrated in these bodies. 



CHEMICAL COMPOSITION OF THE BLOOD. 



In considering the chemical composition of the blood, it will be convenient 

 to take in order the composition of the various chief factors into which the 

 blood may be separated, viz., The Plasma; The Serum; The White Corpuscles; 

 The Red Corpuscles. 



The Composition of the Plasma. The plasma is the liquid part 

 of the blood in which the corpuscles float. 



It contains the fibrin factors, inasmuch as when drawn from the blood 

 vessels it undergoes coagulation and separates into fibrin and serum. It 

 differs from the serum in containing fibrinogen, but in appearance and in 

 reaction it closely resembles that fluid. Its alkalinity, however, is greater 

 than that of the serum obtained from it. It may be freed from corpuscles 

 by the centrifugal machine or by the other means enumerated below. 



The chief methods of obtaining plasma free from corpuscles are: i. By 

 cold. The temperature should be about o C. and may be two or three degrees 

 higher, but not lower. 2. The addition of neutral salts, in certain proportion, 

 either as solids or in solution; e. g., of sodium sulphate, if solid i part to 12 parts 

 of blood; if a saturated solution i part to 6 parts of blood. Or magnesium 

 sulphate, saturated solution i part to 4 of blood. 3. By mixing frog's blood 

 with an equal part of a 5 per cent, solution of cane-sugar, and getting rid of the 

 corpuscles by filtration. 4. By the injection of commercial peptone into the 

 veins of certain mammals previous to bleeding them to death, allowing the 

 corpuscles to subside or by subjecting the blood to the action of a centrifugal 

 machine by the rapid rotation of which the whole of the solids are driven to the 

 outer end of the tubes in which the blood is placed. 



PERCENTAGE COMPOSITION OF PLASMA. 



Water 90.29 



Solids 



1. Proteins 

 Fibrinogen ^ 



Paraglobulin > 8 . 289 



Serum albumin J 



2. Extractives o. 566 



3. Inorganic salts 0.850 



9.71 



100 .00 



Water. The water of the plasma varies in amount according to the 

 amount of food, drink, and exercise or other circumstances. It amounts 

 to about 90 per cent. 



