58 THE HUMAN BODY. 



it is not excreted by the kidneys. The paraglobnlin is also- 

 coagulated by heat, but may be precipitated alone by 

 saturation of the serum with magnesium sulphate. Fats 

 are present in the serum in small quantity except after a 

 meal at which fatty substances have been eaten; serum ob- 

 tained from the blood of an animal soon after such a meal 

 is often milky in appearance from the fats present, instead 

 of being colorless or pale yellow, and transparent as it is after 

 fasting. The salts dissolved in the serum are mainly so- 

 dium chloride and carbonate; small quantities of sodium,, 

 calcium, and magnesium phosphates are also present. 



Chemistry of the Red Corpuscles. In these in the fresh 

 moist state there are in 100 parts, 56 of water and 44 of. 

 solids. Of the solids about one per cent is salts, chiefly 

 potassium phosphate and chloride. The remaining organic 

 solids contain, in 100 parts, 90 of haemoglobin and about & 

 of other proteids; the residue consists of less well-known 

 bodies. 



Chemistry of the White Corpuscles. These yield be- 

 sides much water, several proteids, some fats, glycogen. 

 (see Chap. XXVIII. ), and salts; and smaller quantities of 

 other bodies. The predominant salts, like those of the red 

 corpuscles, are potassium phosphates. 



Variations in the Composition of the Blood. Hygienic 

 Remarks. The above statements refer only to the average 

 composition of the healthy blood, and to its better known 

 constituents. From what was said in the last chapter it is. 

 clear that the blood flowing from any organ will have lost, 

 or gained, or gained some things and lost others, when 

 compared with the blood which entered it. But the losses 

 and gains in particular parts of the Body arc in such small 

 amount as, with the exception of the blood gases, to elude- 

 analysis for the most part: and the blood from all parts 

 being mixed in the heart, they balance one another and 

 produce a tolerably constant average. In health, however, 

 the specific gravity of the blood nmy vary from 1045 to 

 1075; the red corpuscles also are present in greater propor- 

 tion to the plasma after a meal than before it. Healthy 

 sleep in proper amount also increases the proportion of red 



