338 PEACTICAL PHYSIOLOGY 



and serum in small quantities. Thus the blood carries the food 

 materials to the tissues, and the products of metabolism away from 

 them. We have, therefore, in addition to ammonia, small quantities of 

 nitrogenous extractives : urea, uric acid, creatinin, xanthin, hypo- 

 xanthin, etc. ; of non-nitrogenous extractives, fats, cholesterol, lactic 

 acid, and other organic acids. 



In the plasma, too, in very minute quantities, are bodies which play 

 an important part in regulating bodily functions namely, the internal 

 secretions of such glands as the thyroid, parathyroid, suprarenal, 

 pituitary and sexual organs; also such protective bodies as immune 

 bodies, antitoxins, haemolysins and precipitins. 



The percentage composition of the plasma varies with different 

 animals. The following are two analyses : 



Water, - - - - 90-29 \ 



Solids, .... 9-71J 



fibrin, - '40 



- 7-88 



90-80^1 

 9-16J 

 1-01 

 776 



Extractives, - - '56 '52 



Inorganic salts, - - '85 '81 



It will be seen that the amounts of the different proteins present 

 vary in the plasma. This can also be seen from the following table 

 showing the amount in 1000 parts of plasma : 



AnimaL Total protein. Albumin. Globulin. Fibrinogen. 



Man, - - - 72-6 40'1 28 '3 4-2 



Dog, - - - 60-3 31-7 22-6 6'0 



Sheep, - - 72-9 38 '3 30 "0 4-6 



Horse, - - 80 '4 28 "0 47 '9 4-5 



When it is remembered that each of these proteins has probably also 

 a different composition, it can easily be realised how different in 

 composition are the plasmas of different animals (see also chapter on 

 Precipitins, etc.). 



THE CHEMISTRY OF THE LEUCOCYTES. 



These are morphologically the same as other cells, and they contain 

 the same chemical substances. The protoplasm consists mainly of water. 

 The solids consist of various proteins, which chiefly belong to the 

 group of compound proteins (gluco-proteins and nucleo-proteins), and 

 there is also a small amount of albumin and globulin. The protoplasm 

 may also contain such substances as glycogen, fat, mucin, etc., which 

 have either been produced by the activity of the protoplasm, or which 

 are simply deposited in the cell for storage purposes. 



The nucleus seems to consist mainly of nucleo-proteins, nuclein and 

 nucleic acid. The nucleo-protein of the nucleus is said to contain a 

 higher percentage of phosphorus than does that of the protoplasm. 



