PHYSIOLOGY OF THE BLOOD. 



PHYSICAL PROPERTIES OF THE BLOOD. 



The color of the blood varies from bright scarlet-red in the arteries 

 to the deepest dark bluish-red in the veins. Oxygen, therefore also 

 the air, makes it bright red, while deficiency in oxygen renders it dark. 

 The oxygen-free venous blood is dichroic, that is, it appears dark red 

 in reflected light and green in transmitted light. In thin layers the blood 

 is opaque, as one can readily convince himself, if blood be poured 

 upon a glass plate and be permitted to flow off, by attempting to read 

 printed matter through it. The blood thus behaves as a covering 

 pigment, as its coloring matter is suspended in the plasma in the form 

 of small granules, namely, the red blood-corpuscles. 



For this reason the granular coloring matter of the blood can be separated 

 from the blood-plasma by nitration. This, however, is possible only after admix- 

 ture of the blood with fluids that render the blood-corpuscles rough or viscid. If 

 mammalian blood is mixed with one-seventh of its volume of concentrated sodium 

 sulphate, or if frog's blood is mixed with two per cent, solution of cane sugar, and 

 then filtered, the blood-corpuscles will remain upon the filter. 



The reaction of blood is alkaline from the presence of disodium 

 phosphate (Na 2 HPO 4 ). The alkalinity rapidly diminishes in intensity 

 after escape from the vessel, and the more rapidly the greater the pre- 

 vious alkalinity. The change depends upon the development of an 

 acid, in which the red blood-corpuscles take part in consequence of a 

 decomposition of as yet undetermined origin. This generation of acid 

 is increased by high temperature and the addition of alkali. 



The alkalinity of the blood is diminished (A) by active muscular exercise, in 

 consequence of the development of acid in the muscular tissue. (B) By coagulation. 

 Fresh clot has a more intensely alkaline reaction than blood-serum. (C) After the 

 persistent use of soda the alkalinity of the blood is increased, and after the use of 

 acid it is diminished. (D) Old blood or blood dissolved with water from dry- 

 places generally has an acid reaction. The blood of children and women exhibits 

 a lesser degree of alkalinity than that of men, and that of nursing women a lesser 

 degree of alkalinity than that of pregnant women. The alkalinity is less also dur- 

 ing digestion than during fasting. 



Method of Examinat^on. As in consequence of the normal color of the blood 

 red litmus-paper cannot be employed directly in testing the reaction, the following 

 plan is pursued: Blood is mixed with an equal volume of concentrated solution of 

 sodium sulphate, and the mixture is placed upon highly porous and sensitive lilac- 

 tinted litmus blotting-paper. The blood-corpuscles remain upon the surface while 

 fluid is taken up by the paper and gives rise to the reaction. 



For the quantitative estimation of the alkalinity dilute tartaric acid is added 

 to a volume of blood (7.5 grams of crystalline tartaric acid to i liter of water, i 

 cu. cm. of which saturates 3.1 mg. of soda) until the blue paper is reddened. 

 One hundred cu. cm. of human blood contains the alkaline equivalent of from 260 

 to 300 mg. of soda (in guinea-pigs 150 mg., in carnivora 180 mg. of soda). 



Landois' method for the quantitative determination of the alkalinity of the blood 

 with only a few drops of blood : Tartaric acid in the concentration already stated 

 is employed to neutralize the alkalinity of the blood. Of this the following mix- 

 tures are made by addition of concentrated solution of neutral sodium sulphate: 

 (i) 10 parts of tartaric-acid solution and 100 parts of concentrated sodium- 



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