40 PHYSIOLOGICAL EFFECTS 



out running a risk as regards health, which it 

 is well to avoid. You allude to my former 

 warnings briefly given. I have had many a 

 trial in ascending mountains, as I know you 

 have in your wanderings, and though I have 

 not reached the greatest altitudes, I have been 

 on some, as Etna, only second to them. The 

 result of my experience, I may repeat, is that 

 only the young, or at most those of middle life 

 and with vigorous and unimpaired constitutions, 

 should subject themselves to such labours, 

 such trials, and I use the latter word advisedly, 

 for I know no exercise so trying to the vital 

 organs, or more endangering them. How often 

 have I seen even young men, thoroughly over- 

 come in ascending a mountain, and, having 

 reached its summit, throw themselves on the 

 ground, and there remain prostrate till it was 

 time to descend, altogether incapable, from 

 sheer fatigue, of the enjoyment they looked 

 forward to when they set out. In the exertion 

 of ascending, the strain is mainly on the heart, 

 and indirectly through it on the lungs and 

 nervous system, especially the brain. I have 

 made some observations on these occasions on 

 the pulse and respiration, the results of which 



