780 CHEMISTR Y OF RESPIRA TION. 



THE EXCHANGE OF GASES BETWEEN THE BLOOD AND THE TISSUES. 

 INTERNAL EESPIRATION. 



From a comparative study 1 of the process of respiration, it is seen 

 that the exchange of gases in the simplest forms of life is between the 

 external medium and the protoplasm of the cell. 



In insects the smallest branches of the tracheal system carry oxygen to the 

 individual cells, 2 which are often the seat of a most energetic combustion. In 

 no case is this more marked than in the luminous organ of the glowworm 

 (Lampyris splendidula), where, as Max Schultze 3 has shown, there are 

 special cells at the end of the tracheae. The phosphorescence still continues 

 after the removal of the organ from the^nsect's body, and under the microscope 

 is seen to appear first in those parts of the cells which are around the ends of 

 the tracheae. The luminous cells have a great affinity for oxygen, as shown by 

 the fact that they cease to give out light if confined in an atmosphere free 

 from oxygen, 4 and readily reduce osmic acid. 



In the higher animals the blood is the medium which supplies the 

 tissues with oxygen and removes their carbon dioxide and other 

 waste products. Keference has already been made to the theories of 

 Lavoisier and Crawford 5 concerning processes of oxidation in the blood, 

 and we may proceed to consider the experimental evidence which has 

 been advanced in favour of the view, that the blood is the chief seat of 

 combustion. "When blood is shed and kept at the temperature of the 

 body, it becomes gradually poorer in oxygen, 6 and there is always a dis- 

 tinct darkening in the colour of arterial blood, even within the first few 

 minutes after it is shed. 7 These changes were investigated by Pnliger in. 

 a series of determinations of the gases of the blood, and he found that 

 arterial blood received directly into a large vacuum, surrounded by hot 

 water, gave a percentage of oxygen from 0*2 to 10 per cent, higher 

 than the amount extracted by the slower method of the ordinary gas- 

 pump. About the same time Alexander Schmidt 8 found that when the 

 blood of an asphyxiated animal was exposed to a known quantity of 

 oxygen, there was an absorption and disappearance of oxygen, and an 

 increase in the amount of carbon dioxide. The capacity of blood to bring 

 about this oxidation varied ; that taken from contracting muscles could 

 consume from 3 to 4 per cent., that from the heart 2 per cent., and blood 

 from the hepatic vein 0'8 per cent, oxygen. It was sho\vn by Afanassiew 9 

 that only the blood corpuscles and not the serum could take up oxygen 

 in this way, and Tschiriew 10 found that lymph resembled the serum in 

 containing no reducing substances. 



1 See Paul Bert, "Lecons sur la physiologic coinparee de la respiration," Paris, 1870 ; 

 Johannes Miiller, " Elements of Physiology, " Baly's trans., vol. i. ; Pfliiger, Arch.f. d. ges. 

 PhysioL, Bonn, 1875, Bd. x. S. 270. 



2 Finkler, Arch.f. d. ges. PhysioL, Bonn, 1875, Bd. x. S. 273 ; Kupffer, Beitr. z. Anat. 

 u. PhysioL als Festgabe 0. Ludwig, Leipzig, 1875, S. 67. 



3 Arch.f. mikr. Anal., Bonn, 1865, Bd. i. S. 124. 



4 Milne Edwards, " Le9ons sur la physiologie et I'anatomie comparee," tome viii. pp. 

 93-120. 5 See p. 756. 



6 Nawrocki, Stud. d. physiol. Inst. zu Breslau, Leipzig, Bd. ii. S. 144 ; Sachs, Arch. f. 

 Anat., PhysioL u. wissensch. Med., 1863, S. 348. 



7 Pfliiger, Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 61 ; Bernard, Journ. deVanat. 

 et physiol. etc., Paris, 1858, tome i. S. 233. 



8 Bur. d. k. sachs. Gesellsch. d. Wissensch. Math.-phys. CL, Leipzig, 1867, Bd. xix. S. 99 ; 

 Ccntralbl. f. d. med. Wissensch., Berlin, 1867, S. 356. 



9 Ber. d. k. sdchs. Gesellsch. d. Wissensch., Leipzig, 1872, Bd. xxiv. S. 253. 

 10 Ibid., 1874, Bd. xxvi. S. 116. 



