364 RESPIRATION 



to the inspired air. Acapnia may thus be looked on as a contribu- 

 tary cause of the symptoms, so that at first sight there seems to be 

 some experimental support for Mosso's theory. The acapnia, 

 although most important, is, however, only a secondary result of 

 the lowered oxygen pressure. This aspect of the matter has become 

 clear only recently through the work of Kellas, Kennaway, and 

 myself (see Chapter VI), and independently along closely similar 

 lines by that of Yandell Henderson and Haggard. 2 



Mosso held to his acapnia theory till the time of his death, and 

 it was quite in vain that I myself endeavored to persuade him that 

 Paul Bert was right. "Acapnia" became for a time to many 

 physiologists the same sort of ignis fatuus as "reduced alkaline 

 reserve" has been in recent years. In 1906, however, Zuntz and 

 his colleagues placed the main facts in true perspective in an ac- 

 count of investigations carried out at high altitudes in the Alps. 3 



We must now consider acclimatization to high altitudes and 

 anoxaemia caused in other ways. Paul Bert in his book (pp. 336, 

 1105) describes and discusses acclimatization, though he had not 

 himself studied it experimentally. The evidence pointing to the 

 fact of acclimatization was clear. He suggested that the tissues 

 become gradually accustomed to a smaller supply of oxygen in 

 the blood, and perhaps become more economical in their use of 

 oxygen. He also, however, suggests that the oxygen capacity of 

 the blood may become increased at high altitudes; and this he 

 afterwards verified by actual examination of blood taken from 

 animals living at high altitudes. 4 



In 1892 Viault showed that the number of red corpscles per 

 unit volume of blood is increased at high altitudes, and Miintz 

 that the percentage of iron is increased. Various subsequent ob- 

 servers-established clearly the fact that in animals and persons 

 living at high altitudes there is an increase in both the percentage 

 of haemoglobin and the number of blood corpuscles in the blood. 

 By far the most complete and accurate series of observations on 

 the increase in haemoglobin was that carried out in connection 

 with the Pike's Peak Expedition by Miss Fitz Gerald on persons 

 living permanently at different altitudes in the Rocky Mountains 

 and elsewhere in America. Figure 96 shows graphically the 

 average results obtained at different altitudes. 



It will be seen from this figure that on an average the per- 



2 Haggard and Henderson, Journ. Biol. Chem., XLIII, p. 15, 1920. 



8 Zuntz, Loewy, Miiller, and Caspari, HofienkUma und Bergivanderungen, 1906. 



4 Paul Bert, Comptes rendus, XCIV, p. 805, 1882. 



