614 Professor Joseph Barcroft [June 9, 



Haldane, namely, that the want of oxygen heightens the activity 

 respiratory of the respiratory centre, resulting in a mild degree of 

 forced respiration — so mild as not to be apparent to the subject, yet 

 sufficient to reduce the carbon dioxide content of his blood. 

 Incidentally this process acting alone would make the blood more 

 alkaline. The measurements of hydrogen ion concentration in the 

 blood of persons at rest bore out this view ; either the blood was 

 more alkaline than at sea level, or it was of approximately the same 

 reaction. 



The effect of exercise on the blood has been more fully investi- 

 gated, though for the most part by indirect methods. Our results 

 support those already obtained, namely, that a given increment in 

 the hydrogen ion concentration of the blood is produced by less 

 exercise at high altitudes than at the sea level. Thus the dyspnoea 

 of exercise is the cumulative effect of two factors — an increased 

 response of the respiratory centre to a given stimulus, and an increase 

 in the stimulus evoking the response. 



3. I have already alluded to the size of the Cholo's chest. With 

 it appears to be associated an interesting modification of its configura- 

 tion. Fig. 2 shows two X-ray photos of the left sides of two chests 

 photographed from behind. Both pictures were made at Cerro de 

 Pasco. That on the right is my own, and is fairly typical of our 

 party ; that on the left is a typical Cholo chest. There is a marked 

 difference in the angle at which the ribs are carried ; my own slope 

 down from the vertebral column at a quite considerable angle, while 

 those of the native are much more horizontal. It seems highly 

 probable that this horizontal carriage of the ribs indicates a com- 

 pensatory effort designed to increase the facility with which the 

 blood obtains oxygen, for it is acquired at sea level by persons 

 suffering from emphysema and other complaints in which there is 

 shortness of breath. Several of the mining engineers, of whose 

 chests we took radiograms, showed a similar tendency. At this point 

 another peculiar physical conformation may be mentioned, namely, 

 clubbing of the fingers, which, when found at sea level, is frequently 

 associated with some trouble which prevents sufficient oxygen from 

 reaching the extremities. Though they are not the rule, clubbed 

 fingers are by no means unusual at Cerro de Pasco iu persons 

 without any circulatory or respiratory lesion. 



4. An increase in the number of red blood corpuscles in each 

 cubic mm. of blood has long been known to occur at high 

 altitudes. Systematic researches carried out principally under the 

 direction of Dr. Haldane have shown that the increase in the number 

 of red blood corpuscles is associated with an increase in the quantity 

 of haemoglobin present. These two observations we have verified, 

 and to them have added a third, namely, that the chemical con- 

 ditions under which the haemoglobin is held in the red blood 

 corpuscle confer on it the peculiarly useful property of acquiring 



