CHEMISTRY OF RESPIRATION. 



BY M. S. PgMBREY. 



CONTENTS : Historical, p. 692 Respiratory Changes in Air-Methods, p. 694 

 Conditions affecting Respiratory Exchange, p. 700 Cold-Blooded Animals, p. 

 701 Fishes, p. 704 Warm-Blooded Animals, p. 706 Influence of External 

 Temperature, p. 709 Of Muscular Activity, p. 714 Of Food, p. 717 Of Size 

 of Animal, p. 720 Of Time of Day, p. 721 Of Age, p. 722 Respiration by 

 Skin in Amphibia, p. 723 In Mammals, p. 725 Effects of Varnishing Skin, 

 p. 727 Respiration in Alimentary Canal, p. 728 Respiration of Foetus, 

 p. 730 Of Embryo, p. 733 The Respiration of different Gases, p. 735 The 

 Respiration of Vitiated Air, p. 741 Asphyxia, p. 743 Exchange of Gases 

 between Blood and Air, p. 745 Frequency of Respiration in Man, p. 747 In 

 Animals, p. 753 Changes in Composition of Air, p. 754 Effect of Respiration 

 on Blood, p. 756 Gases of Blood- Methods, p. 757 Arterial and Venous Blood, 

 p. 760 Condition of Gases in Blood, p. 765 Causes of Gaseous Exchange 

 between Blood and Air, p. 773 Exchanges of Gases between Blood and 

 Tissues, p. 780 Causes of such Exchange, p. 783. 



EESPIRATION is essentially the intake of oxygen and the output of 

 carbon dioxide by living cells. In the higher animals two phases of 

 respiration are distinguished the external, the exchange of gases between 

 the air or water and the blood ; and the internal, the exchange between 

 the blood, lymph, and the tissues. 



Historical Account. 1 The view held by Aristotle (384-322 B.C.), and 

 after him even until the fifteenth century, was that respiration drew air into the 

 heart and arteries, and so cooled the blood. Malpighi (1621-1694) discovered 

 the alveoli of the lungs, and saw the blood flowing through the capillaries of 

 the alveoli of a frog's lung; and Fracassati, 2 in 1665, noticed that the lower 

 layer of a blood clot was much darker in colour than the upper, but that on 

 exposure to the air the lower became florid red. Hook 3 showed the following 

 experiment at a meeting of the Eoyal Society in 1667. The ribs and diaphragm 

 of a dog were cut away, and the trachea connected with a pair of bellows. 

 The dog fell into convulsions, but revived when air was blown into the lungs. 

 Numerous small holes were now made in the surface of the lungs, and by means 

 of two bellows the lungs were kept constantly distended with fresh air ; the 

 dog lay still, and its heart beat regularly. A piece of lung was cut off, and it 

 was noticed that the blood circulated even when the lungs were collapsed. 

 Hook therefore came to the conclusion that the cause of death was not the 

 stoppage of the circulation, but the want of a sufficient supply of fresh air. 

 Croon 4 had previously shown before the same Society a similar experiment ; 



1 For further details see Bostock's "Physiology," 2nd edition, 1828, vol. ii. p. 61; 

 Paul Bert, "Lecons sur la physiol. comp. de la respiration," Paris, 1870, p. 1; Zuntz, 

 Hermann's "Handbuch," Bd. iv. Th. 2, S. 5. 



2 Phil. Trans., London, 1667, p. 492. 3 Ibid., 1667, p. 539. 

 4 Dcrham's "Physico-Theology," 4th edition, 1716, p. 146. 



