152 HANDBOOK OP PHYSIOLOGY. 



Inorganic Substances In 1,000 parts of plasma there are 



Chlorine 3.536 



Sulphuric acid . ... .129 



Phosphoric acid . 145 



Potassium ,,.,.. .314 



Sodium , 3.410 



Phosphate of lime .298 



Phosphate of magnesia , . . . . .218 



Oxygen .455 



8. 505 



(2.) The Serum. The serum is the liquid part of the blood or of 

 the plasma which remains after the separation of the clot. It is a trans- 

 parent, yellowish,, alkaline 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. 



Serum may be obtained from blood corpuscles by allowing blood to 

 clot in large test tubes, and subjecting the test tubes to the action of a 

 centrifugal machine (rig. 133) for some time. 



In tabular form the composition may be thus summarized. In 1000 

 parts of serum * there are: 



Water , about 900 



Proteids : 

 a. Serum-albumin ....... ) 



(3. Serum-globulin . . . . . . . v 80 



7. Fibrin ferment \ 



Salts. 



Fats including fatty acids, cholesterin, lecithin ; and 

 some soaps 



Grape sugar in small amount 



Extractives creatin, creatinin, urea, etc. 

 Yellow pigment, which is independent of hgemoglobin. 

 Gases small amounts of oxygen, nitrogen, and carbonic 

 acid 



> 20 



1000 



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

 the amount of food, drink, and exercise, and with many other circum- 

 stances. 



b. Proteids. . Serum albumin is the chief proteid found in serum. 

 The proportion which it bears to serum-globulin, the other proteid, is 

 as 3 to 4.5 in human blood. 



Serum-albumin has been shown by Halliburton to be a compound 

 body which may be called serins, made up of three proteids, which 



*This table is more detailed than that of the plasma given above The 

 salts, extractives, etc., are the same in both serum and plasma, but the proteids 

 are somewhat different in nature and amount. 



