This question regarding the salts actually occurrint in the blood is however far from settled, Ludwig having positively denied Enderlin's statements. (Day's 'Report on the Progress of Chemistry,' in Ranking's ' Ilalf-Yearly Abstract of the Medical Sciences,' vol. iii., 1846.) Generally speaking it is only requisite in the analysis of the blood, to determine a few of the most important constituents; as, for instance, the water, fibrin, blood-corpuscles (globulin and hmtnatin), and the solid residue of the serum (the organic portion and the salts). For this purpose we may adopt the following simple plan lately published by Figuier. It is based on the fact made known many yearn ago by Berzelius, that after the addition of a solution of a neutral salt to dofibrinated blood, the globules do not (ns before) pass through filtering paper. On the addition of two parts of a solution of sulphate of soda of specific gravity 1.130 to one of blood, Figuier found that the whole of the corpuscles remained on the mut-face of the filter. The following are the steps of his analysis :—The fibrin is removed by stirring, dried, and weighed; the weight of the corpuscles is ascertained by the method indicated, and that of the albumen by coagulating by means of heat the filtered solution. The proportion of water is known by evaporating a small known weight of the blood. The filter containing the corpuscles should be dipped in boiling water, which removes any sulphate of soda that may be present, and at the same time renders the corpuscles insoluble. Separate and frequently difficult processes are requisite to detect those ingredients which occur in small quantity or only in morbid conditions.
With regard to the distinctions between Arterial and Venous Blood, we have already noticed the circumstance that the external envelope of the blood-corpuscles becomes converted during the act of respiration into oxidised protein, mid that the bright-red colour of arterial blood is owing in part to the modifying influence of the white investing membrane. But there is yet another mode in which it acts. The huffy coat, which is the name given to the superimposed layer of fibrin in the clot, is frequently observed on the upper part of the clot in inflammatory diseases as being very apt to curl up and become concave. Now this huffy coat consists, for the most part, of the oxides of protein—of the very same matter with which the blood corpuscles become invested. For this reason the form assumed by the two laminae on both sides of the little flat body—the corpuscle— must resemble that of the Iniffy coat. The tendency to contract and become biconcave is so strong, that the central portion of the crust becomes entirely depressed. In this form the corpuscles reflect a great deal more light than when, in consequence of the removal of the huffy coat in the capillaries, they have a less hi-concave form.
From four analyses of the blood of horses, Simon deduces the following rule regarding the chemical differences of arterial and venous blood :—"Arterial contains lean solid residue generally than venous blood ; it manilla lean fat, less albumen, less litematin, leas extractive matter and salts, than venous blood. The blood-corpuscles of arterial blood contain less colouring matter than those of venous blood." The arterial blood was taken from the carotids, and the venous from the jugulars.
In a medical point of view the composition of venous blood is the most interesting, because it is from the veins that blood is almost always taken in disease, and because venous blood can naturally only be compared with venous blood for the purpose of ascer taining any deviations that may occur. The following table repre
sents the mean composition of human venous blood without reference to sex : Water . ..... Solid Constituents . . . . Fibrin . ..... Fat Albumen Globulin • Hmmatin . ..... . 6/09 Extractive Matters and Salts . . . 100 parts of blood-corpuscles contain 5.7 of larematin.
Hence the blood contains about 20 per cent. of solid constituents, much more than 0.2 per cent. of fibrin, and about an equal quantity of fat ; the blood-corpuscles considerably exceed the albumen in quantity, and contain about 5 or 6 per cent. of colouring matter.
The blood undergoes various modifications in different forms of disease. The extent of these variations is obvious from the following table, drawn up from Simon's 'Animal Chemistry,' vol. 1, p. 246.
The Water may vary from . . . . to The Solid Residue „ . . . . . to The Fibrin . . . . to a trace.
The Fat 4-3 to The Albumen . 13P0 to The Globulin to 30-8 The Haematin„ . . . . 81 to The Extractive Matters and Salts . . . 16.5 to The following synopsis will give an idea of the distribution of the constituents of the blood.
Water 790'37 Albumen 67'80 Oxygen . . . . Nitrogen . . . .
Carbonic Acid. . Serum 869'15 Extractive Matter Fatty Matter .
Salts . . . .
Colouring Matter Fibrin . 2'95 Haemutin . 2-27 Blood corpuscles 127'90 Clot Globulin . 1000.00 1000.00It will be seen from the previous account that the blood is one of the most important constituents of the body. It is in fact the prime source of life, and is the great medium through which the constituents of the body pass in their way from the vegetable and mineral kingdoms to become part and parcel of the tissues of the body. The food is taken up from the intestines [Fool)] by the lacteals, and is converted into blood before it is appropriated in the tissues of the body. The correspondence between the flesh or tissues of the body and the blood may be ken in the following statement of the ultimate composition of the two.
Blood.
Carbon . . . . . 51.86 51'96 Hydrogen . . . . . 7-58 7/5 Nitrogen 15'03 15'07 Oxygen . . . . 2P30 21'30 Ash . . . . . 4 /3 4.42 The blood ie not only the source whence the tissues are supplied with the fresh materials for their growth, but it is the means by which effete matters are thrown off from the system. The con stituents of the bile, the urine, the perspiration, the expired air from the lungs, are all found in the blood, and separated from it by the liver, kidneys, skin, and lungs. The changes involved in the formation of these excretions are some of them important to life, as that of carbonic acid gas during respiration [RESPIRATION], which is attended with the development of animal heat.
Any interruption or impediment to the performance of the functions of the blood is attended with disease. This has long been suspected, but it is only since the employment of the microscope and chemical analysis that any advance has been made in studying the relation of abnormal conditions of the blood to particular diseases of the body.
(Hunter, On the Blood ; Sharpey, Quain's Anatomy, vol. i.; Simon, Animal Chemistry, translated by Day; Milne-Edwards, article 'Blood,' in Cyclopadia of Anatomy and Physiology ; Lehmann, Physiological Chemistry, translated 4'y Day; Liebig, Animal Chemistry; Carpenter, Human Physiology).