200 PHYSIOLOGY. 



feverish period of cholera, in which the urinary secretion is sup- 

 pressed, provoke the accumulation of urea in the blood. 



Gases. Oxygen, carbon dioxide and nitrogen are present. The 

 oxygen is united to the haemoglobin of the red corpuscle. 



The combinations of carbonic acid in the blood are much more 

 complex than those of oxygen. In 100 cubic centimeters of arterial 

 blood carbonic acid is associated as follows: 



1 to 2 cubic centimeters of C0 2 dissolved in plasma. 



35 to 40 cubic centimeters of C0 2 in combination in plasma. 



10 cubic centimeters of C0 2 in the corpuscles. 



Carbonic acid dissolved in the plasma exists in a state of carbo- 

 nate and bicarbonate, in the red corpuscles in a state of phospho- 

 carbonate of sodium and carbo-haemoglobin. 



The nitrogen is simply dissolved in the plasma. 



Blood-serum. Blood-serum is blood-plasma minus fibrinogen. 

 Serum contains serum-globulin, serum-albumin and fibrin-ferment 

 (nucleo-proteid.) Serum is a liquid, slightly viscid, of a yellow 

 color, or may be milk-like in color if the diet has been rich in fat, 

 due to the presence in it of fat, and has a saline taste. The amount 

 of serum is a third or a half of the whole quantity of blood. The 

 substances in 'the serum, like in the plasma, are sodium and potas- 

 sium chloride, potassium sulphate, sodium and calcium phosphates, 

 magnesium phosphate and sodium carbonate. The chief salt of 

 these is sodium chloride, forming nearly one-half of the inorganic 

 salts. The quantity of salt is about 8 parts in a 1000. The quan- 

 tity of sodium chloride in the blood is very constant. In animals 

 deprived of sodium chloride the proportion of salt in the blood 

 diminishes very little. The kidneys excrete very little. If, how- 

 ever, a large amount of salt is taken it is rapidly eliminated by the 

 kidneys. The importance of having a fixed amount of sodium 

 chloride always in the blood is the necessity to preserve the osmotic 

 pressure. 



The Serum-albumin and Serum-globulin of Serum. They have 

 the general characteristics of the albumins and globulins. In star- 

 vation the quantity of serum-albumin diminishes, that of serum- 

 globulin increases. Besides these bodies there is also found a small 

 quantity of nucleo-proteid in the serum: 



Sugar. One part in a 1000 is also found here. 



Fat. The quantity of fat in the blood varies very much. It 

 swings between 1 to 7 parts in a 1000 in the dog. The fatty mat- 

 ters are neutral fats, soaps and lecithin. The fat acids are found 



