Studies of blood formation and destruction in the polycythemia of high altitude have been carried out. Three different groups of subjects were studied:

1. Healthy adult male subjects from sea level who, after being studied at this level, were taken to an altitude of 4,540 meters (Morococha) where they developed a marked polycythemic process. When these subjects returned to sea level, the mechanisms of recuperation of the hematologic equilibrium were studied.

Normal adult subjects, natives of high altitude, chronically polycythemic due to their permanent residence in Morococha, who were first studied in their native town and then brought to sea level where they were observed during five weeks.

3. Subjects, residents of high altitude (Morococha), who had lost their adaptation to it; i.e. who had developed chronic altitude sickness or Soroche (Monge's malady).

The observations carried out permit the following conclusions:

1. The polycythemic process of subjects with anoxia caused by a low pressure environment is due to a greater blood formation by the hematopoietic organs. This becomes manifest after forty-eight hours. The very discreet polycythemia frequently found during the first hours is probably the result of hemoconcentration and release of stored blood.

2. This polycythemic process is not accompanied by quantitative alterations of the leukocytes nor of the platelets; thus, differing from polycythemia vera, in which there is as a rule an increase in all the hematologic elements.

3. The increased blood volume of residents at high altitude is due exclusively to the increased red cell mass, the plasma volume being more likely to be found diminished.

4. In normal subjects who are temporarily or permanently exposed to an atmosphere of low barometric pressure, the excretion of fecal urobilinogen does not exceed the limits considered normal at sea level, but increases with relation to the larger circulatory hemoglobin mass, a normal hemolytic index being maintained.

5. The hyperbilirubinemia very frequently found in the natives and in those resident for a long time at high altitudes appears to be related to a lesser excretion of this pigment by the liver, probably on the basis of the anoxic state. The greater production of bilirubin in subjects at high altitude is not sufficient to explain, in and of itself, the pigmentary elevation in the blood.

6. The mechanism of the disappearance of the polycythemia when the subjects from a high altitude are brought to sea level, appears to be as follows: (a) temporary diminution or inhibition of erythropoiesis, and (b) a greater blood destruction. The latter takes place only during the first days of stay at sea level, being chiefly responsible for the early rapid decrease of the degree of polycythemia, while the former acts in a more prolonged form and is principally responsible for the erythropoietic "normalization."

7. In two cases of chronic altitude sickness, or chronic Soroche (Monge’s disease), the output of fecal urobilinogen exceeded proportionally the increase of the circulatory hemoglobin mass. The hemolytic index was found abnormally high.

8. The above findings indicate that the polycythemia of the normal individual residing at high altitudes is characterized by a proportional and direct accentuation in the processes of blood formation and destruction. On the other hand, in those subjects also residing at high altitudes, who exhibit an abnormally high polycythemia (chronic Soroche), the accentuation in the processes of blood destruction is proportionally greater than that corresponding to the greater erythropoiesis. This characteristic constitutes a possible diagnostic criterion and can perhaps explain in part the etiologic mechanism of this alteration.