402 



NATURE 



\August 23, 1888 



so that the blood now contained 23-4 per cent, by volume instead 

 of 20 per cent. These facts indicate that when all the haemo- 

 globin has been satisfied with oxygen it becomes indifferent, 

 within limits, to any additional oxygen that may be forced into 

 the blood under pressure, and thus the blood of animals breathing 

 an atmosphere richer in oxygen than ordinary air is not more 

 highly oxygenated than normal blood. The practical result also 

 follows that it is of no use in the treatment of disease to cause 

 patients to breathe an atmosphere richer in oxygen than ordinary 

 air, because, at ordinary atmospheric pressure, no more oxygen 

 can thus be caused to enter the blood, and if it be desirable to 

 hyperoxygenate the blood, this can only be done by breathing 

 oxygen, under a pressure of three or four atmospheres, in a 

 chamber in which the body of the patient is subjected to the 

 same pressure. 



In this connection it is important to notice the enormous ab- 

 sorptive surface for oxygen presented by the red blood corpuscles 

 of man. There are about 5,000,000 red corpuscles in each 

 cubic millimetre. Each corpuscle has a superficial area of 

 0*000128 square millimetre. Taking the blood in the body of 

 a man of average size at 4/5 litres, that is 4,500,000 cubic milli- 

 metres, the number of corpuscles is about 22,500,000,000,000, 

 and this would give a superficial area of 2,880,000,000 square 

 millimetres, or 2880 square metres, or about 315 1 square yards 

 — that is to say, the absorptive area of the blood corpuscles is 

 equal to that of a square having each side about 56 yards. The 

 haemoglobin in a red blood corpuscle amounts to about \% of its 

 weight. The blood of a man of average size may be taken at 

 4536 grammes, or about 10 pounds. Such blood contains about 

 i3 - o83 per cent, of haemoglobin, and 4536 grammes will con- 

 tain about 593 grammes of haemoglobin, or about ii pound. 

 As regards the iron, which is supposed to be an essential consti- 

 tuent of haemoglobin, 100 grammes of blood contain 00546 

 gramme. It follows that the total amount, 4536 grammes, 

 contain about 2-48 grammes, or nearly 39 grains. Twenty-five 

 minims of the tinctura ferri perchloridi contain about 1 grain 

 of pure iron, so it will be seen that not many doses are required 

 to introduce into the body an amount of iron as large as exists 

 in the whole of the blood. 



The absorption of oxygen, therefore, probably takes place as 

 follows : the inspired air is separated in the alveoli of the lung 

 by delicate epithelial cells and the endothelial wall of the 

 pulmonary capillaries from the blood which circulates in the 

 latter. The exchange of gas takes place through these thin 

 porous membranes, so that the velocity of the transit must be 

 practically instantaneous. As the oxygen is bound loosely to 

 the haemoglobin of the corpuscles, the laws of diffusion can have 

 only a secondary influence on its passage, and only so far as it 

 has to pass into the plasma so as to reach the blood-corpuscles. 

 The plasma will absorb, at 35° C, about 2 volumes per cent., if 

 we take the coefficient absorption of the plasma as equal to that 

 of distilled water. Many of the blood corpuscles of the pulmon- 

 ary blood have just returned from the tissues with their haemo- 

 globin in the reduced state, and the latter at once withdraws 

 oxygen from the plasma. In an instant more oxygen passes out 

 of the pulmonary air into the plasma, from which the oxygen is 

 again quickly withdrawn by the haemoglobin of the corpuscles, 

 and so on. It is interesting to note that, if the oxygen did not 

 exist in loose chemical combination, it would only be absorbed, 

 and its amount would depend on the barometrical pressure at 

 the moment, and would follow each fluctuation of pressure 

 through a range, say, of one-fourteenth of the total pressure. 

 Such an arrangement could not fail in affecting health. If, on 

 ascending a high mountain, say 15,000 to 20,000 feet above the 

 level of the sea, the pressure sank to nearly one-half, the blood 

 would then contain only half its normal quantity of oxygen, and 

 disturbances in the functions of the body would be inevitable. 

 High-flying birds, soaring in regions of the air where the 

 pressure falls below half an atmosphere, would suffer from want 

 of oxygen ; but in deep mines and on high mountains men and 

 animals live in a state of health, and the quick-breathing bird 

 has a sufficient amount of oxygen for its marvellous expenditure 

 of energy, because the amount of oxygen in the blood is inde- 

 pendent of the factor which exercises an immediate influence on 

 the gas contents of the fluid— namely, the partial pressure. 

 Kempner has also proved that so soon as the amount of oxygen 

 in the respiratory air sinks only a few per cent, below the 

 normal, the consumption of oxygen by the tissues and the forma- 

 tion of carbonic acid also fall in consequence of the processes of 

 oxidation in the body Decoming less active. 



■It is a remarkable fact that, in certain circumstances, tissues 



and even organs may continue their functions with little or no 

 oxygen. Thus, as quoted, Max Marckwald, in his work on the 

 " Innervation of Respiration in the Rabbit " (translated by 

 T. A. Haig, with introduction by Dr. McKendrick ; Blackie 

 and Son, 1888): " Kronecker and MacGuire -found that the 

 heart of the frog pulsates just as powerfully with blood deprived 

 of its gases as with that containing oxygen, while the blood of 

 asphyxia, or blood containing reduced haemoglobin, soon stops 

 its action." 



Further, Kronecker has found that dogs bear the substitution 

 of two-thirds to even three-fourths of their blood by 06 per- 

 cent, solution of common salt, and Von Ott withdrew 14/15 

 of the blood of a dog, and replaced the same with serum from 

 the horse, free from corpuscles. For the first day or two after 

 the transfusion the dog had only 1/55 part of the normal 

 number of red blood corpuscles, so that it had only 1/55 part 

 of its normal amount of oxygen. But this dog showed no 

 symptoms except weakness and somnolency, nor did it suffer 

 from distress of breathing, a remarkable fact when we consider 

 that the blood of an asphyxiated dog still contains 3 per cent, of 

 oxygen, and that it may show great distress of breathing when 

 there is still one-sixth part of the normal amount of oxygen in 

 its blood. 



The conditions regulating the exchange of carbonic acid are 

 quite different. We have seen that the carbonic acid is almost 

 exclusively contained in the blood plasma, the smaller part being 

 simply absorbed, and the greater part chemically bound, a portion 

 existing in a fairly firm combination with a sodic carbonate of 

 the plasma, and another portion in a loose, easily decomposable 

 combination with the acid sodium carbonate, and a third portion 

 with the sodium phosphate Carbonic acid is contained in air 

 only in traces, and its tension in the air is almost nothing. The 

 air contained in the lungs is not wholly expelled by each respira- 

 tion, but a part of the air of expiration, rich in carbonic acid, 

 always remains in the lung. It is evident, then, that by the mixing 

 of the air of inspiration with the air in the alveoli, the latter will 

 become richer in oxygen and poorer in carbonic acid. The air 

 in the alveoli, however, will always contain more carbonic acid 

 than atmospheric air. Pfliiger and Wolff berg have found the 

 amount of carbonic acid in alveolar air to be about 3 "5 volumes 



\ 'c x 760 



per cent., therefore its tension will be — — =27 mm. of 



100 



mercury. The tension of the carbonic acid in the blood of the 

 right ventricle (which may be taken as representing venous 

 pulmonary blood) amounts, according to Strassburg, to 5-4 per 

 cent. — 41 mm. of mercury, and is 14 mm. higher than that in 

 the alveoli. Carbonic acid will, therefore, pass by diffusion 

 from the blood into the alveolar air until the tension of the 

 carbonic acid has become the same in the blood and in alveolar 

 air. Before the state of equilibrium is reached, expiration begins 

 and removes a part of the air out of the alveoli, so that the 

 tension of the carbonic acid again becomes less than that in the 

 blood. During the expiration and the following pause, the 

 elimination of carbonic acid continues. This physical arrange- 

 ment has the advantage for diffusion, that by expiration the whole 

 air is not driven out of the lungs, for, if expiration had emptied 

 the lungs of air, the diffusion would have ceased altogether 

 during expiration and the following pause, and diffusion have 

 been possible only during inspiration. There would thus have 

 been an incomplete separation of the carbonic acid from the 

 pulmonary blood. But as air remains in the lungs, the stream 

 of diffusion between pulmonary blood and pulmonary air goes on 

 steadilv, and fluctuations occur only in regard to its velocity 

 (Munk). 



Any account of the gaseous constituents of the blood would be 

 incomplete without a reference to the ingenious theory recently 

 advanced by Prof. Ernst Fleischl von Marxow, of Vienna, 

 and explained and illustrated in his work " Die Bedeutung des 

 Herzschlages fiir die Athmung ; Eine Neue Theorie des Respira- 

 tion,'"' a work distinguished alike by the power of applying a pro- 

 found knowledge of physics to physiological problems, and by a 

 keen and subtle dialectic. The author starts with the antagonistic 

 statements that of all animal substances, haemoglobin is the one 

 which possesses the greatest affinity for oxygen, or that sub- 

 stances exist in the animal body which, at least occasionally, have 

 a greater chemical affinity for oxygen than haemoglobin possesses. 

 If the tissues have a greater affinity for oxygen than haemoglobin 

 has, how is it that in the blood of animals that have died of 

 asphyxia there is still a considerable quantity, in some cases as 

 much as 5 volumes per 100 volumes, of oxygen ? It is well known 

 ■ that the blood of such animals invariably shows the spectrum ot 



