2 PHYSICAL PROPERTIES OF THE BLOOD. 



temperature and the addition of an alkali favour the formation of the acid (A 7 . 

 Zunt::). 



The alkaline reaction of blood is diminished : (o) by great muscular exertion, owing to the 

 formation of a large amount of acid in the muscles ; (/8) during coagulation ; (7) in old blood, 

 or blood dissolved by water from old blood-stains, such blood being usually acid ; fresh cruor 

 has a stronger alkaline reaction than serum ; (5) after the prolonged use of soda the alkalinity 

 is increased, after the use of acids it is decreased. 



Methods. Owing to the colour of the blood we cannot employ ordinary litmus paper to test 

 its reaction. One of the following methods may be used: (1) Moisten a strip of glazed red 

 litmus paper with .solution of commou salt, and allow a drop of blood to fall on the paper ; 

 then rapidly wipe it off before its colouring matter has time to penetrate and tinge the paper 

 [Zuatiz). (2) Liebreich used thin plates of plaster-of-Paris of a perfectly neutral reaction. 

 These are dried, and afterwards moistened with a neutral solution of litmus. When a drop of 

 blood is placed upon the porous plate, the fluid part of the blood passes into it, while the 

 corpuscles arc washed off with water, ami the altered colour of the litmus-stained slab is 

 apparent. [(3) Schafer uses dry faintly-reddened glazed litmus paper, and on it is placed a 

 drop of blood, which is wiped off after a few seconds. The place where the blood rested i 

 indicated by a blue patch upon a red or violet ground.] 



Estimation of the Alkalinity. A very dilute solution of tartaric acid (1 cubic centimetre 

 combines with 3*1 milligrams of soda, i.e., 1 litre of water contains 7 '5 grains of crystallised 

 tartaric acid) is added to blood until a blue litmus paper is turned red (by Zuntz's method). 

 100 grams of rabbit's blood have an alkalinity corresponding to 150 milligrams of soda ; the 

 blood of carnivora to about 180 milligrams (Lassar), while 100 c.c. of normal human blood have 

 an alkalinity equal to 260-300 milligrams of soda (v. Jaksch). 



The following method can be used with a few drops of blood : To neutralise the blood, tar- 

 taric acid in the above concentration is used. Prepare the following mixture by mixing it with 

 a concentrated neutral solution of sodic sulphate, and then adding sodic sulphate until the 

 mixture is completely saturated. I., 10 parts of solution of tartaric acid to 100 parts of con- 

 centrated sodic sulphate solution ; II., 20 parts tartaric acid solution to 90 sodic sulphate solu- 

 tion ; III. contains these substances in the proportion of 30 to 80 ; IV., 40 to 70 ; V., 50 to 

 60 ; VI., 60 to 50 ; VII., 70 to 40 ; VIII., 80 to 30 ; IX., 90 to 20 ; and X., 100 to 10. Excess 

 of sodic sulphate is present in all the flasks. 



A known volume of the blood to be investigated is mixed with an equal volume of each of 

 the mixtures, in a small tube, which is made by drawing out a glass tube 1 millimetre in 

 diameter to a fine point. To calibrate this tube, suck up water, say, to the height of 8 mm., 

 make a mark on the tube with a fine file, then suck up the water until its lower level corre- 

 sponds with the mark. Again mark the upper limit of the water. To test the blood, suck a 

 drop of the mixture I. up to the level of the first mark on the glass pipette, and, after wiping 

 its point, suck up an equal quantity of blood. Again clean the point of the pipette, and blow 

 its contents into a watch-glass ; then mix, and test the reaction with sensitive violet-coloured 

 litmus paper. Proceed in the same way with the several mixtures, II., to X., until the 

 alkaline reaction disappears or the acid appears. The narrow strips of litmus paper are dipped 

 into each of the mixtures, the corpuscles remain in the wetted part of the paper, while the 

 fluid permeates further and shows the reaction. As a rule, the degree of alkalinity in human 

 blood corresponds to VI. Human blood can be sucked directly from a small wound made 

 by a needle, either by attaching an elastic tube or a small hypodermic syringe to the pipette 

 (Landois). 



Pathological. The alkalinity is increased during persistent vomiting, and decreased in 

 pronounced amemia, cachexia, uremia, rheumatism, high fever, diabetes, and cholera. [Imme- 

 diately before death by cholera it may be acid (Cantani).] 



(3) Odour. Blood emits a peculiar odour, the halitus sanguinis, which differs 

 in animals and man. 



It depends upon the presence of volatile fatty acids. If concentrated sulphuric acid be added 

 to blood, whereby the volatile fatty acids are set free from their combinations with alkalies, the 

 characteristic odour, somewhat similar to that of butyric acid, becomes much more perceptible. 



(4) Taste. Blood has a saline taste, depending upon the salts dissolved in the 

 fluid of the blood. 



(5) Specific Gravity. The specific gravity is 1056-1059 in man, 1051-1055 

 in woman ; in children less. The specific gravity of the blood-corpuscles . is 1105, 

 that of the plasma 1027. Hence the corpuscles tend to sink. 



Clinical Method. A thin glass tube is drawn out till it is of small calibre, and then bent at 

 a right angle, and closed above with a caoutchouc cap. Press sligljtly on the caoutchouc cap, 

 and suck up a drop of the freshly-drawn blood obtained by pricking the finger. The fine capil- 



