J90 



NA TURE 



[January 26, 1899 



which is available, but on the necessities of the animal ; 

 variations between i2'5 and 60 per cent, of oxygen have 

 scarcely any intluence on the magnitude of the gas- 

 exchanges in respiration. 



Though most of the evidence in this book is not in 

 favour of the idea that there is an ano\yha;mic condition 

 of the blood at great altitudes, the new theories which 

 are advanced can only be accepted when more experi- 

 mental work has been accomplished. As to the changes 

 in the blood on the Alps, on the question whether the 

 undoubted increase in number of red corpuscles is real 

 or apparent, Prof. Mosso is in accord with many physio- 

 logists in considering that the cause of the variations 

 lies in the climatic conditions, in the more active influence 

 of the sun's rays, in the greater dryness of the air, and 

 in the altered mode of life. His own observations on this 

 subject, which is one of the greatest interest, are open to 

 the objection which may be taken to so many of the facts 

 in this book, that the method of conducting the experi- 

 ments is described, but the description is insufficient to 

 enable a fair criticism to be made as to the value of the 

 work. His contention that if Suter found an increase of 

 64 per cent, in the number of red corpuscles at a height 

 of 1300 feet, the blood of those on Monte Rosa should 

 show an increase of 64 per cent., which he regards as 

 absurd, might possibly be found to be the case, since 

 X'iault's figures for a lower level showed an increase of 

 3,000,000 corpuscles per cubic millimetre of blood. 



The cause of mountain-sickness is maintained by Prof. 

 Mosso to be due to an actual diminution in the quantity 

 of carbonic acid in the blood, the theory of acapnia, 

 which assumes that this gas is the normal exciting agent 

 for causing a discharge from the nerve-cells in the 

 medulla oblongata. Mountain-sickness is in fact an 

 asphyxia that is dependent not upon want of oxygen, 

 but on a want of carbonic acid. He affirms that mountain- 

 sickness is generally worse at night, and that this is due 

 to a diminished production of carbonic acid when a man 

 is at rest. The experience of many climbers is the con- 

 trary ; mountain-sickness may occur quite suddenly 

 during an ascent. There are members of the Alpine 

 Club who have never reached the summit of Mont 

 Blanc even after repeated attempts ; a limit of 13,000 feet 

 on this mountain cannot be passed without exceeding 

 distress. The same individuals can, however, reach the 

 summit of .Monte Rosa. That there is really a deficiency 

 of carbonic acid in the blood at great heights is most 

 difficult of proof. Prof. Mosso refers to the analyses of 

 the blood-gases made by Kraenkel and Geppert in 1883, 

 and though these may show a slight decrease in the 

 amounts of the carbonic acid, the differences are almost 

 within the limits of experimental error. There is no 

 fixed figure which decisively gives the actual amount of 

 this gas in the blood. .At the sea-level the amount of 

 carbonic acid in arterial blood of the same species of 

 animal may vary from 4263 to 23-9 per cent, or from 

 53'4 to 23'3 per cent. If Prof. .Mosso uses selected cases 

 from Fraenkel and Geppert's tables in order to strengthen 

 his position, it may be pointed out that their analyses 

 show that with a rarefied atmosphere corresponding to 

 23,000 feet, the blood may actually contain more carbonic 

 acid than at the sea-level. Even if it could be shown by 

 NO. 1526, VOL. 59] 



data far more convincing than those given by Prof. 

 Mosso, that there is an alteration in the output of 

 carbonic acid at great heights, we should not be justified 

 in regarding this as evidence of an alteration in the 

 carbonic acid of the blood. To advance one hypothesis 

 against another, it is conceivable that since an organism 

 with excess of carbonic acid in the blood strives to 

 eliminate this by increased frequency of breathing, an 

 organism that possesses less of this valuable gas in its 

 blood would tend to preserve a constant percentage in 

 this liquid by exhaling, first of all, a less amount, and 

 perhaps at last hardly any of the gas, in the same way as 

 an animal is known to preserve the proteid constituents 

 of its body at the expense of the fats and carbohydrates 

 during starvation. 



In the experiment on p. 298, where it is shown that 

 the effects of diminished pressure may be counteracted 

 by administration of air with 167 per cent, of carbonic 

 acid, there would appear to be an error, for if the gas- 

 mixture was made as is described, the original air of the 

 laboratory must have contained 8 per cent, of carbonic 

 acid. As to the action of this gas on the organism, 

 according to Prof. Mosso's e.xperiments, it essentially 

 produces a slackening of the cardiac movements, which 

 is seen not at the sea-level, but when the organism is 

 subjected to the action of rarefied air. It may be ad- 

 mitted that there is a prompt reaction to a slight increase 

 of carbonic acid in inspired air, and comparatively none 

 to the same proportional diminution of oxygen, but since 

 it is not possible to show that a slight excess or diminu- 

 tion of oxygen in inspired air is followed by any e.xcess- 

 or diminution of this gas in the blood, it is probable that 

 the effect of an increase of carbonic acid in inspired air 

 acts in a reflex manner, and not by an action on some 

 part of the central nervous system after it has been 

 absorbed by the blood. That definite constriction of 

 the bronchioles occurs as the result of a reflex action 

 after the inhalation of small percentages of carbonic 

 acid is a well-established fact, and there is every prob- 

 ability, or at any rate the possibility, which Prof. Mosso 

 does not discuss, that an increased percentage of carbonic 

 acid acts in a similar way. In the pneumatic chamber 

 Prof. Mosso has succeeded in withstanding a rarefaction 

 of the air when the barometer stood at 192 mm. This 

 corresponds to an altitude of 37,862 feet. .\t the com- 

 mencement of the experiment the pressure was 742 mm. 

 .A.fter about an hour, when the pressure is 292 mm., 

 oxygen is inhaled by allowing about 100 litres of the gas 

 to enter the pneumatic chamber. The pulse rate has 

 fallen below the normal, the heart beats 64 per minute, 

 and the rate of respiratory rhythm is 19. Half an hour 

 later, at a pressure of 192 mm, the pulse is 84 and 

 respiration 18. The oxygen percentage by weight in the 

 chamber at 292 mm. was 8'45 before o.xygen was allo^ved 

 to flow in, and 814 parts by weight when the pressure 

 had fallen to 192 mm. The air of the chamber now- 

 contained 2' I per cent, of carbonic acid, but contained 

 only '8 per cent, of this gas when the pressure was 

 292 mm. Prof. Mosso's interpretation of this interesting 

 experiment is that he sustained a diminution of pressure 

 from 292 to 192 mm., on account of the presence of this 

 21 per cent, of carbonic acid. Though he admits that 



