V 



THE BLOOD: PLASMA 



131 



The small amount of glycogen that can lie demonstrated in 

 blood serum (Pavy) probably derives from the disintegration 

 of the leucocytes, which, as stated, contain a certain amount 

 of it. 



The constant presence of lactic acid in blood serum is in- 

 dependent of the ingestiou of carbohydrates, while it is, on the 

 contrary, partly dependent on the flesh food. The amount of 

 lactic acid found in the blood of dogs during absorption after a 

 full meat meal, may amount to 0'3-0'5 per cent, while after 

 forty-eight hours' starvation it diminishes to 017 per cent 

 (Gaglio). Lactic acid, as we shall see, is one of the decomposition 1 

 products of proteins, elaborated either by the blood corpuscles or 

 by the living elements of the various tissues. 



V. The mineral constituents of blood plasma occur partly in 

 the form of free salts, partly in combination with the proteins, 

 from which they cannot be separated by simple dialysis. 

 What the true physical and chemical conditions within the 

 plasma the reciprocal relations and the fixed or labile bonds 

 between the various mineral constituents on the one hand, and 

 the various proteins on the other may be, is one of the most 

 difficult problems in the chemical physiology of to-day, and its 

 solution is the aim of various physico-chemical researches, of 

 which this is not the place to speak. 



If combustion is employed to isolate the inorganic matters 

 from the dry residue of serum, the ash will be found to contain 

 a large amount of sulphates, derived from the combustion of the 

 sulphur of the proteins, which are not among the mineral con- 

 stituents of true plasma. In the same way, if care be not taken 

 before the serum is incinerated to remove the lecithin by ether, 

 there will, owing to combustion of its phosphates, be an excessive 

 increase in the phosphates of the ash. 



Setting aside for these reasons the sulphates and phosphates 

 found in the ash of serum, the results of the different analyses 

 made for man and for the other mammals harmonise perfectly for 

 the rest of the constituents, as appears from the following table : 



