The current belief in regard to the effect of residence at altitudes on the composition of the blood postulates an interesting physiologic adaptation of the organism to the decreased oxygen tension of the atmosphere at the higher levels. In a general way it is most commonly explained that, as an immediate effect of change to a region of low atmospheric pressure, there is a relative increase in the red blood corpuscles due to a concentration of the blood and a diminution of its plasma. Simultaneously, however, the blood-forming organs enter into a condition of increased activity, so that, after a stay of some duration at a height, both red corpuscles and hemoglobin are considerably increased in total amount.
The physiologic significance of such an increase in the oxygen-carrying capacity of the blood, when an atmosphere of low oxygen tension is breathed, is obvious. The differences in views on the subject