440 BLOOD AND LYMPH. 



altitudes may be compensated by an increased amount of hemo- 

 globin, and subsequently Viault* demonstrated that living for a 

 short time at very high altitudes (4000 meters) causes a marked in- 

 crease in the number of red corpuscles, an increase, for instance, 

 from 5,000,000 per c.mm. to 7,000,000 or even 8,000,000. This fact 

 has since been investigated with great care by a large number of 

 observers and under a great variety of conditions: The observation 

 has been abundantly confirmed, and indeed it would seem that the 

 reaction takes place very quickly. Within twenty-four hours, 

 according to some observers, and in less time, according to others 

 who have experimented during balloon ascensions (Gaule, Hallion, 

 ana Tissot). the increase in the number of corpuscles may be de- 

 tected, although the maximum increase comes on more gradually. 

 According to Kemp, f the number of blood plates is also greatly 

 increased by high altitudes, while the leucocytes are not affected. 

 There has, however, been much difference of opinion as to whether 

 this increase in number of the red corpuscles is relative or absolute, 

 that is, whether the total number of red corpuscles in the blood, 

 and therefore probably the total amount of hemoglobin, is increased, 

 or whether it is simply an apparent increase due, for instance, to a 

 diminution in the water of the blood and a consequent concentration 

 as regards the number of corpuscles, or to a variation in the distri- 

 bution of the corpuscles between the vessels of the skin and those 

 of the internal organs. The results published upon these questions 

 have been conflicting. According to one set of observers there is 

 an absolute increase in the total number of red corpuscles, and 

 therefore in the total amount of hemoglobin. There seems to be 

 little doubt that such a change occurs in cases of long residence 

 in high altitudes, and we may assume that the diminished amount 

 of oxygen in the air or some other condition peculiar to these 

 altitudes acts as a stimulus to the blood-forming tissues (red mar- 

 row) and augments the output of corpuscles and hemoglobin. 

 The increase in number of corpuscles and percentage of hemo- 

 globin occurs slowly upon changing from a low to a high altitude, 

 and their inverse change upon returning to a low altitude also 

 occurs gradually. An illustration of the relationship between 

 altitude and amount of hemoglobin is given in Fig. 185a. Ac- 

 cording to another set of observers, the increase in the number 

 of red corpuscles is due to a concentration of the blood. The 

 blood-plasma is reduced in quantity, perhaps by transuda- 

 tion of water into the tissues, and, therefore, the number of red 

 corpuscles and the amount of hemoglobin become greater for each 

 cubic millimeter. If we assume that this smaller bulk of blood, 

 more concentrated in corpuscles and hemoglobin, circulates 



* Viault, "Comptes rendus de 1'academie des sciences," 1890 and 1891. 

 f Kemp, "American Journal of Physiology," 10, 34, 1904. 



