THE INCREASE IN THE NUMBER OF 
ERYTHROCYTES WITH ALTITUDE. 
By Captain HUGH W. ACTON, I.M.S., and Major W. F. HARVEY, I.M.S., 
Pasteur Institute, Kasauli. 
The subject has previously been investigated by numerous observers and their 
work has invariably shown that there is a definite increase in the number of 
erythrocytes in the peripheral blood with a change of altitude. Most of the 
investigations have however, been conducted either on animals alone, or on 
a small number of human beings. We. on our part have carried out these 
investigations on biometric lines in order to determine the undermentioned 
points : — 
(1) The normal variations in the number of erythrocytes in apparently healthy 
individuals. 
(2) The effect that a high altitude has on this number. 
(3) The effect, if any, that a change of altitude has on anaemic individuals. 
The opportunities that were afforded to us to investigate these points were 
unique in many ways, as we had access to a considerable number of more or less 
healthy individuals (Natives of India) and furthermore they remained on the spot 
some 18 — 20 days whilst undergoing anti-rabic treatment (Hogyes dilution 
method). 
This treatment may possibly affect the leucocyte content of the blood but there 
is no evidence to show that it has any influence on the erythrocyte content, and 
therefore should not lead to any alteration in our findings on that account. 
Kasauli is a hill station in the Punjab in India situated in the Sub-Himalayan 
range, Lat. 30° 58' 4", Long. 77° 2' 3" and 6335 feet (about 1920 metres) above 
sea-level. The patients examined numbered 127 all told ; they were taken in the 
order they came for treatment and were all adult men. Cases severely bitten and 
those suffering from inflammatory conditions, as the result of the bite, were 
excluded. We may therefore affirm that the men represented a varied sample 
of the population. Our patients came from all parts of Burmah, Assam, Central 
