908 EDWAED C. SCHNEIDER 



hemoglobin in the blood of the body; (2) a fall in the lung alveolar carbon 

 dioxid partial pressure and a rise in the alveolar oxygen pressure, the 

 result of increased ventilation of the lungs due to deeper breathing ; and 

 (3) at some altitudes a temporary or permanent increase in the rate of 



blood flow. 



The Blood Adaptive Changes. In spite of an occasional contrary 

 observation the prediction made by Paul Bert in 1878 that the blood at 

 high altitudes would be found to have a greater oxygen capacity than the 

 blood of similar individuals at lower levels, has been demonstrated to be 

 true. Investigators have found an increase in the number of red corpuscles 

 per cubic millimeter and in the percentage of hemoglobin. Miss Fitz- 

 gerald (a) (6), by a study of inhabitants of the Southern Appalachian and 

 the Rocky Mountains, found that as the altitude increases the percentage 

 of hemoglobin in the blood is augmented about 10 per cent of the normal 

 value, for men and women at sea level, for every 100 mm. fall of barometric 

 pressure. The physiological significance of this increase in hemoglobin 

 and red corpuscles is that a unit volume of blood can carry for a given 

 oxygen pressure more oxygen than normally. 



When a rapid ascent -is made to a high altitude, as in an aeroplane, 

 the changes in the blood may be detected as early as in from 20 to 60 

 minutes. When the ascent is made more slowly, as by automobile or 

 railway, it may not be evident for 12 or more hours. The increase is 

 rapid for the first two to four days and is followed by a more gradual 

 increase extending over a period of six weeks. The increase occurs most 

 rapidly in subjects in excellent physical condition. Fatigue, as from 

 walking up a mountain, delays the increase in hemoglobin and red 

 corpuscles. 



At the present time the evidence accounts for the increase in hemo- 

 globin and erythrocytes as follows: the initial rapid increase is due to a 

 concentration by a loss of fluid from the blood and possibly by throwing 

 into the general circulation a large mass of reserve corpuscles. The more 

 gradual increase, extending over several weeks, is brought about by the 

 increased activity of the bone marrow resulting in an increase in the total 

 number of corpuscles and amount of hemoglobin which may finally not 

 only restore, but sometimes actually increase, the low altitude blood 

 volume. 



The number of leukocytes per cubic millimeter is not increased with 

 altitude, but the larger lymphocytes are increased and the polymorpho- 

 nuclear cells diminished. The blood platelets are also increased at high 

 altitudes. 



Respiratory Adaptation to High Altitudes. The first effects observed 

 on going to a high altitude are caused by an insufficient supply of oxygen 

 to the tissues. It is to be expected, therefore, that the amount of air 

 pumped in and out of the lungs will be increased almost immediately. 



