250 Chapter XVII 



the problem of getting your equipment there is much more simple. 

 You put it on the steamer, with due leisure, in Liverpool, London or 

 Southampton, and you take it off at Santa Cruz. If you do not mind 

 travelling in a steamer of 2000 tons, you may disembark under the very 

 windows of the Hotel Humbert and have your things carried up by 

 the hotel porter. We were fortunate enough at Teneriffe to be passed 

 through the customs the same consideration, indeed, was shown to the 

 Monte Rosa expedition, for which I should like, here and now, to record 

 my thanks to the Ambassadors of France and Italy : yet, even taking 

 these acts of encouragement to scientific workers into consideration, 

 the difficulty of getting your apparatus intact to Col d'Olen is very 

 great. Think of the embarking and the disembarking on the channel 

 steamer, think of the terrors of the custom house, even if the luggage 

 is unopened, of the justifiable resentment of your fellow-passengers if 

 you take it in bulk in the railway carriage and of the impossibility of 

 putting it in the van ; delicate as my apparatus was, I brought all the 

 important pieces back intact from Teneriffe : little but broken glass 

 arrived in London from Col d'Olen. 



But, perhaps, the greatest advantage of Teneriffe is that you can 

 start your work at the sea-level. On our Monte Rosa expedition we 

 made Pisa our base of operations. This, of course, is a far cry from 

 Col d'Olen as compared with the mule ride from Orotava to the 

 Canadas that perhaps is a minor consideration and would not be a 

 consideration at all if Turin were made the base but there seemed 

 to me a much greater difference between the climate of the plains of 

 Tuscany and that of the high Alps than exists between Orotava and 

 the Canadas. In the latter case there was the difference in the 

 moisture, upon which we have already touched, but the difference 

 in the temperature nothing near so great. 



In spite, however, of these differences, altitude clearly had an 

 effect which was the same in both cases. There were two obvious 

 changes, both of them well known from the work of previous authors, 

 which must, in some way, affect the amount of oxygen in the 

 arterial blood both of these are evident from a study of the alveolar 

 air. The first is the diminished oxygen pressure in the inspired air, 

 the second the diminished carbonic acid pressure in the expired air. 

 Of these two, the latter shall claim our interest first. 



Great stress was laid by Mosso upon the diminished CO, in the 

 breath, not because its diminution is of any importance in the breath, 

 but because this is but the reflection of lowered CO 2 pressure in the 



