MICEOSCOPIC EXAMINATION OF THE BLOOD. 3 



lary-tube is at once immersed in a solution of sodic sulphate, and a drop of tlie blood expressed 

 into the saline solution. It is necessary to prepare several solutions of sodic sulphate with 

 specific gravities varying from 1050-1070. The solution in which the corpuscles remain 

 suspended indicates the specific gravity of the blood {Roy, Landois). 



The drinking of water and hunger diminish the specific gravity temporarily, while thirst and 

 the digestion of dry food raise it. If blood be passed through an organ artificially, its specific 

 gravity rises in consequence of the absorption of dissolved matters and the giving off of water. 

 It falls after haemorrhage, and is diminished in badly-nourished individuals. [By working 

 with solutions of glycerine, Jones finds that it is highest at birth, is at a minimum between the 

 second week and the second year ; it rises gradually until the 35th-45th year. It is usually 

 higher in the male than the female, is diminished by pregnancy, the ingestion of solid or liquid 

 food, and gentle exercise.] 



[(6) Temperature. Blood is viscid, and its temperature varies from 36-5 C. 

 (97-7 F.) to 37-8 (100 F.). The warmest blood in the body is that of^ the 

 hepatic vein ( 210).] 



2. MICROSCOPIC EXAMINATION. [Blood, when examined by the microscope, 

 is seen to consist of an enormous number of corpusclescoloured and colourless 

 floating in a transparent fluid, the plasma, or liquor sanguinis. 



Fig. 1. 

 A, human coloured blood-corpuscles 1, on the flat; 2, on edge ; 3, rouleau of coloured cor- 

 puscles. .B, amphibian coloured blood-corpuscles 1, on the flat ; 2, on edge. C, ideal 

 transverse section of a human coloured blood-corpuscle magnified 5000 times linear ab, 

 diameter ; cd, thickness. 



Human Red Blood-Corpuscles. (a) Form. They are circular, coin-shaped, 

 homogeneous discs, with saucer-like depressions on both surfaces, and with rounded 

 margins ; in other words, they are bi-concave, circular non-nucleated discs. 



(b) Size. The diameter (ab) is 7'7/x, 1 (6'7-9'3/x) the greatest thickness (cd) l*9/x 

 (fig. 1, C), [i.e., it is ^ua * 32V0 ^ an i ncn i* 1 diameter, and about one-fourth of 

 that in thickness]. 



They are slightly diminished in size by septic fever, inanition, morphia, increased bodily 

 temperature, and CO a ; and increased by O, watery condition of the blood, cold, consumption 

 of alcohol, quinine, and hydrocyanic acid. Compare 10, 3. 



If the total amount of blood in a man be taken at 4400 cubic centimetres, the corpuscles 

 therein contained have a surface of 2816 square metres, which is equal to a square surface with 

 a side of 80 paces ; 176 cubic centimetres of blood pass through the lungs in a second, and the 

 blood-corpuscles in this amount of blood have a superficies of 81 square metres, equal to a square 

 surface with a side of 13 paces ( Welcker). 



(c) The weight of a blood-corpuscle is 0*00008 milligramme. 



1 The Greek letter fi represents one-thousandth of a millimetre (/i = 0*001 mm.), and is the 

 sign of a micro-millimetre, or a micron. 



