QUANTITY OF BLOOD, AND ITS DISTKIBUTION IN THE BODY. 53 



36. The red corpuscles contain lees water than the serum, the amount 

 of solid matter being variously estimated at from 30 to 40 or more per cent. 

 The solids are almost entirely organic matter, the inorganic salts amounting 

 to less than 1 per cent. Of the organic matter again by far the larger part 

 consists of haemoglobin. In 100 parts of the dried organic matter of the 

 corpuscles of human blood, about 90 parts are haemoglobin, about 8 parts 

 are proteid substances, and about 2 parts are other substances. Of the 

 last, one of the most important, forming about a quarter of them and 

 apparently being always present, is lecithin. Cholesterin appears also to 

 be normally present. The proteids which form the stroma of the red cor- 

 puscles appear to belong chiefly to th^ globulin family. As regards the 

 inorganic constituents, the corpuscles are distinguished by the relative 

 abundance of the salts of potassium and of phosphates. This at least is 

 the case in man ; the relative quantities of sodium and potassium in the 

 corpuscles and serum respectively appear, however, to vary in different 

 animals ; in some the sodium salts are in excess even in the corpuscles. 



37. The proteid matrix of the white corpuscles we have stated to be 

 composed of myosin (or an allied body), paraglobulin and possibly other 

 proteids. The nuclei contain nuclein. The white corpuscles are found to 

 contain, in addition to proteid material, lecithin and other fats, glycogen, 

 extractives and inorganic salts, there being in the ash, as in that of the red 

 corpuscles, a preponderance of potassium salts and of phosphates. 



The main facts of interest then in the chemical composition of the blood 

 are as follows : The red corpuscles consist chiefly of haemoglobin. The or- 

 ganic solids of serum consist partly of serum-albumin, and partly of para- 

 globulin. The serum or plasma contrasts, in man at least, with the corpus- 

 cles, inasmuch as the former contains chiefly chlorides and sodium salts, 

 while the latter are richer in phosphates and potassium salts. The extrac- 

 tives of the blood are remarkable rather for their number and variability 

 than for their abundance, the most constant and important being perhaps 

 urea, kreatin, sugar, and lactic acid. 



THE QUANTITY OF BLOOD, AND ITS DISTRIBUTION IN THE BODY. 



38. The quantity of blood contained in the whole vascular system is a 

 balance struck between the tissues which give to, and those which take away 

 from, the blood. Thus the tissues of the alimentary canal largely add to the 

 blood water and the material derived from food, while the excretory organs 

 largely take away water and the other substances constituting the excretions. 

 Other tissues both give and take, and the considerable drain from the blood 

 to the lymph spaces which takes place in the capillaries is met by the flow 

 of lymph into the great veins. 



From the result of a few observations on executed criminals it has been 

 concluded that the total quantity of blood in the human body is about T ^th 

 of the body weight. But in various animals, the proportion of the weight 

 of the blood to that of the body has been found to vary very considerably 

 in different individuals ; and probably this holds good for nian also, at all 

 events within certain limits. 



In the same individual the quantity probably does not vary largely. A 

 sudden drain upon the water of the blood by great activity of the excretory 

 organs, as by profuse sweating, or a sudden addition to the water of the blood, 

 as by drinking large quantities of water or by injecting fluid into the blood- 

 vessels, is rapidly compensated for by the passage of water from the tissues 

 to the blood, or from the blood to the tissues. As we have already said, the 

 tissues are continually striving to keep up an average composition of the 



