1922] on Physiological Effects at High Altitudes in Peru 611 



ference of the Anglo-Saxons was little in excess of Dreyer's estimate. 

 The lowest level at which we came across one of these small people 

 with chests which appeared out of proportion to the rest of his 

 stature was at Matucana (8000 ft.), and on inquiry we found that 

 he was a native of Huancayo (12,0<)() ft.). 



To pass to the more strictly physiological aspects of the work 

 of the expedition, one must reflect that the desire to investigate 

 mountain sickness goes back at least to the middle of the last century. 

 It is remarkable, when one comes to think of it, how recently our 

 knowledge of the causation of disease has grown. The lure of 

 mountain sickness to the physiologist lay originally in the fact that 

 it was a disease to which a definite cause could be assigned. You go 

 a certain height up the mountain — any mountain— and when your 

 ascent corresponds to a given fall in the barometer you suffer from 

 mountain sickness ; when you descend, the malady leaves you. 

 Mountain sickness, or, as it is called in Peru, " seroche," seemed to 

 form a sort of opening into the aetiology of disease. 



In recent years the centre of interest has to some extent shifted. 

 The cause of mountain sickness is universally regarded as insufficient 

 oxygen supply to the tissues of the body, though there may still 

 be some doubt as to the directness of the connection between the 

 deficiency of oxygen pressure in the blood and the activity of the 

 nerve cells responsible for the continence of food in the stomach. 

 Interest latterly has centred rather around the methods which the 

 body has at its disposal for adapting itself to such a condition. But 

 the same thread still runs through the fabric ; this particular 

 instance of adaptation to environment is studied because our know- 

 ledge of the conditions with which the body has to deal are so exact 

 and the conditions themselves so easily produced or abolished. 



Partly, of course, it has another interest, namely, that imperfect 

 oxygenation of the blood is a factor in a number of pulmonary com- 

 plaints, and an analysis of those complaints demands an investigation 

 of this particular factor. That is the definitely medical aspect, of 

 which I shall say but little. Eather I shall turn my attention to the 

 extent to which adaptation can take place, and the means by which 

 it is brought about. 



Some of the Cholos appear at first sight to have acquired an 

 astonishing capacity for physical effort at high altitudes. An example 

 may be cited. Near Cerro de Pasco there is a mine worked in the 

 old Spanish way. The ore is raised from the bowels of the earth on 

 the backs of porters, who carry their loads up a rude staircase. The 

 mine is about 250 ft. below the surface, and the staircase about 

 650 ft. in length. It opens under a sort of hut. The first porter 

 whom we saw emerge was a little fellow, who said that he was ten 

 years old. We so far doubted his word as to place his age at thirteen 

 or fourteen years. He had on his back a load of ore which I 

 estimated at 40 lbs, — and that at an altitude at which the barometer 



