64 THE ACTIVE FORCES OF LIVING ORGANISMS 



to some extent tend to reduce metabolism. Experi- 

 ments in the pneumatic chamber show, as might be 

 expected, that the amount of carbonic acid expired in 

 the first half -hour is far greater than can be obtained 

 afterwards, even though the pressure be very greatly 

 diminished, so that the ultimate effect of greatly 

 decreased pressure, when prolonged, is to lessen not 

 only the actual amount of carbonic acid in the blood, 

 but also the production of it, or in other words to 

 retard metabolism. 



The com- Many who have made a special study of the con- 

 position of 

 the blood dition of the blood in high altitudes concur in the 



in high .... 



altitudes. Opinion that it contains, as a rule, a greater propor- 

 tion of hemoglobin, whilst some aver that the red 

 corpuscles are also greatly increased in number. 

 Although Mosso does not share these views, and 

 expresses doubt, which is perhaps to a certain extent 

 justifiable, as to the reliability of the experiments 

 undertaken by the various observers, yet one can 

 scarcely refuse to recognise the general probability 

 of the facts asserted. If one be right in supposing 

 that chemical action is retarded and rendered less 

 intense as we rise in altitude above a certain height, 

 that in other words the life stream is rendered less 

 rapid, the sojourn in the system for a longer period 

 of iron and other chemical substances becomes not 

 only explicable but natural. Chlorophyll, one of the 

 chief sources of iron for grass-eating animals, is prob- 

 ably the same at all levels, but the rate of excretion 

 would depend on that of the vital processes in general. 



