EFFECT OF ALTERED AIR PRESSURE 267 



haemoglobin content of the blood is increased, as in the case of 

 acclimatisation to high altitudes ? 



TABLE XLVI. 



ATMOSPHERIC PRESSURE AND NUMBER OP ERYTHROCYTES. 



Height above sea Red 



level in metres. corpuscles. 



Christiania 4,970,000 



Zurich 412 5,752,000 



Davos 1560 6,551,000 



Arosa 1800 7,000,000 



Cordilleras 4392 8,000,000 



Hasselbalch shows that the hydrogen ion concentration is 

 increased under those circumstances. 



' This question of secretion by the lungs is instructive from the point 

 of view of ' vitalism.' When first proposed, it was held to apply to 

 the ordinary state of affairs ; but as improvements were made in experi- 

 mental methods, the absorption was shown to follow physical lines ; 

 it was then held to apply to cases of muscular exercise, and now only 

 to acclimatisation to high altitudes. One might venture to say that the 

 more accurate the methods of investigation the better is it found that 

 chemical and physical laws are capable of explaining physiological pheno- 

 mena."- Bayliss, Principles of General Physiology. 



Let us now consider what happens to the inland transport 

 service when the port becomes congested with incoming traffic. 

 Compressed air is used in all the great sub-aqueous works of to-day, 

 in diving, in preparing foundations for bridges, in pier building, and 

 in the construction of tunnels or shafts through water-bearing 

 strata. It is well known that a large percentage of the men 

 working under those conditions suffer illness and many die. In 

 the construction of the Adour bridge 90 per cent, of the workers 

 suffered from " compressed air " disease, and in the boring of the 

 Hudson Tunnel 2 per cent, of the caisson workers died each month. 

 Compressed air sickness is characterised by its protean symptoms 

 loss of speech, blindness, deafness, transitory madness, vertigo, 

 loss of consciousness, emphysema, spinal paralysis, etc. None 

 of the symptoms, with the exception of some slight ear trouble, 

 ever occurs while the men are under pressure. " Mules lived about 

 a year in the Hudson tunnel and were healthy enough to kick and 

 bite at allcomers." The illness seemed to come on during or 

 after decompression and is now known to be due to the appearance 

 of bubbles of nitrogen in the tissues. Boyle, in the seventeenth 

 century, showed that bubbles of gas appeared in the humours of a 

 viper's eye when submitted to rapid decrease of air pressure under 



