THE BLOOD. 



85 



Salts of the Plasma. In 1000 parts plasma there are: 



Sodium Chloride 



Soda . 



Sodium Phosphate 



Potassium chloride . 

 " sulphate . 

 Calcium phosphate 

 Magnesium phosphate 



5-546 

 1-532 

 271 

 359 

 281 

 298 

 218 



8.505 



Serum. The serum is the liquid part of the blood or of the plasma 

 remaining after the separation of the clot. It is an alkaline, yellowish, 

 transparent fluid, with a specific gravity of from 1025 to 1032. In the 

 usual mode of coagulation, part of the serum remains in the clot, and the 

 rest, squeezed from the clot by its contraction, lies around it. Since the 

 contraction of the clot may continue for thirty-six or more hours, the 

 quantity of serum in the blood cannot be even roughly estimated till this 

 period has elapsed. There is nearly as much, by weight, of serum as 

 there is clot in coagulated blood. 



Chemical Composition of the Serum. 



Water 



Proteids: 



a. Serum-albumin 



ft. Paraglobulin ...... 



Salts. 



Fats including fatty acids, cholesterin, lecithin; 

 and some soaps 



Grape sugar in small amount ... 



Extractives kreatin, kreatinin, urea, etc. 



Yellow pigment, which is independent of haemo- 

 globin ........ 



Gases small amounts of oxygen, nitrogen, and 

 carbonic acid 



about 900 



80 



20 



1000 



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

 amount of food, drink, and exercise, and with many other circumstances. 

 Proteids. a. Serum-albumin is the chief proteid found in serum. 



It is precipitated on heating the serum to 140 F. (60 C.), and 

 entirely coagulates at (167 F. 75 C.), and also by the addition of strong 

 acids, such as nitric and hydrochloric; by long contact with alcohol it is 

 precipitated. It is not precipitated on addition of ether, and so differs 

 from the other native albumin, viz., ^(/-albumin. When dried at 104F. 

 (40 C.) serum-albumin is a brittle, yellowish substance, soluble in water, 

 possessing a Isevo-rotary power of 56. It is with great difficulty 



