Volume 1

The practice of medicine / by Thomas Hawkes Tanner.

  • Thomas Hawkes Tanner
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: The practice of medicine / by Thomas Hawkes Tanner. Source: Wellcome Collection.

    33/692 (page 5)
    SECT. I.] by the red blood-corpuscles; so that a transudation of gases takes place as the blood in its flow through the pulmonary capillaries becomes exposed to the influence of the atmosphere in the cavities of the air cells. The alteration from arterial to venous blood occurs in the systemic capillaries, and is due to the haemoglobin yielding up the oxygen associated with it_, and becoming charged with car- bonic acid. The theory, that in the act of respiration a combina- tion or perfect oxidation took place in the lungs, owing to the oxygen from the air uniting with the carbon from the blood and forming carbonic acid, has been abandoned. It has been shown by the experiments of Bernard, Fernet, Pfliiger, Bert, and others, that the oxygen of arterial blood is held almost exclusively bj'^the red corpuscles in loose chemical combination with the haemoglobin, while the carbonic acid of venous blood is found mainly in the liquor sanguinis partly in solution, but chiefly in combination with the phosphate and carbonate of soda. According to the researches of Pettenkofer on the elimination of carbonic acid and the absorp- tion of oxygen by day and by night, it appears that large quantities of carbonic acid are formed during the day, while the absorption of oxygen at this time is comparatively small. But at night, during repose, a considerable quantity of oxygen is absorbed; which instead of being at once used up for oxidation, is, as it were, stored away in the system, ready for the wants of the ensuing day. The process of oxidation has many intermediate stages ; and these occupy the oxygen for some hours within the system, before it is finally eliminated in the form of carbonic acid and water. Life is only to be maintained by the circulation of arterial blood; and whether no blood circulates through the arteries, oi merely venous blood, the result is the same—death. When no blood circulates, death is said to take place from si/ncope; and this is of two kiads. Firstly, death by ancsmia, in which there is a want of the due supply of blood to the heart, as is witnessed in fatal haemorrhage, &c. j secondly, death by asthenia, where there is a failare in the contractile power of the heart, which may arise from injury or disease of the heart itself or from some cause operating through the nervous system, as from the action of certain poisons, from intense grief or terror, from lightning, concussion of the brain or spine, blows on the epigastrium, as well as from certain forms of apoplexy. It must be remembered that in some in- stances dissolution is due partly to anaemia and partly to asthenia; as may be particularly noticed in fatal cases of starvation, and in lin gering disorders like phthisis, dysentery, &c. When venous blood circulates through the arteries, life will be destroyed in one of two ways. In the first place we have death by asphyxia, or more correctly speaking by apnma ['A = priv. + ttvem = to breathe], or suffocation, where the access of air to the lungs is prevented; as occurs in drowning, strangulation, choking, immo- bility of the respiratory muscles from tetanus, section of the