An introduction to human physiology / by Augustus D. Waller.

  • Waller, Augustus.
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to human physiology / by Augustus D. Waller. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    II. THE BLOOD ^roteich, carbo]iydnites,fitt, salts. Living tissues are constantly in a state of chemical change, consuming and assimilating to themselves materials which they derive from the blood, and rejectmg the consequent Avaste products. These are discharged mto and earned away by the blood, which contains, therefore, the materials m their used-up form, viz. carbonic acid and urea. In correspondence with the large proportion of proteids and of hgemoglobin contained in blood, the elementary composition of its solid residue agrees closely with that of proteids in general, and with that of muscle, which is essentially proteid. A com- parison of some actual analyses, giving the amounts of the chief elements entering into the composition of blood, muscle, hamo- Elementary composition (in the dried state) Of Blood Of Muscle Of HKmoglobin Of Proteids Carbon . ' . 51-96 51-86 53-8 51-5 to 54-5 Oxygen .... 21-30 21-30 21-2 20-9 to 23-5 Hydrogen 7-25 7-58 7-1 6-9 to 7-3 Nitrogen.... 15-07 15-03 16-1 15-2 to 17 Physical properties.—Blood in the body, or freshly drawn, is a slightly viscid fluid, bright scarlet in colour if taken from an artery, dark purple or almost black if taken from a vein ; in either case opaque, even in thin layers. It is heavier than water, its specific gravity being about 1,050 as compared with water, 1,000 —i.e. 1,000 cubic centimeters of water weigh 1,000 grammes, 1,000 cubic centimeters of blood will weigh about 1,050 grammes;' its reaction is alkaline, never acid—the popular expression ' acidity of the blood ' has no foundation in fact. The alkalinity varies in degree ; it is at a maximum after meals, owing to the secretion of acid gastric juice, and at a minimum after severe exertion, owing to the acid which is formed in muscular con- traction ; the alkalinity of blood is attributable to the presence ' Measurements will be given throughout according to the metric system. 1 gramme = about 15 grains. 100 cubic centimeters, or 100 c.c. = about 3| fluid ounces. For microscopic measurements the unit is the micromillimeter, or l^t = ^oVo millimeter = about ir^jm inch. The preliminary difliculties generally experienced by students in the use of metric measurements are soon overcome, and their greater simplicity appreciated. The relative magnitudes 8m, lO^i, 15u, SOju are far more readily realised than the corresponding values in., ^i-^u in-. tiuJo in., in- The capacities of vessels used in the practical classes are marked on the metric system, and students soon learn that a 100 c.c. flask holds rather less than a 4-oz. bottle, and that a 500 c.c. Leaker is the equivalent of a short pint.