U9 



Tlie second part of tlie paper will comprehtind an inquiry into 

 tlie special character and properties of the two colourable principles, 

 the Erythrogen and Xanthogen. 



J2. On DvspiHPa, and otiier Sensations experienced on the 

 sunuiiit of IMont I<lanc. By Martin Barry, M. D. 

 Communicated by I)r Alis(;n. 



Tiiirst and loss of appetite were tlie first symptoms experienced 

 by Dr Barry at a height of about 14,000 feet; but it was not till 

 he reached a height 1000 feet greater, that exhaustion and fatigue 

 supervened. A tendency to fainting was felt, and a total indiflfe- 

 rence to the main object of the journey. After a few minutes of 

 rest, these sensations disappeared, but were again perceived on 

 proceeding a few steps. On the summit (15,666 feet above the 

 sea; Barom. 17.052, Detached Therm. 30°) no particular lassi- 

 tude was felt while the author performed his experiments. After 

 the descent the anthor did not suffer from a state of collapse. 



It was shewn, that of those who have ascended Mont Blanc and 

 other high mountains, some have suffered more, others less, — that 

 there have been differences in this respect, not only among indivi- 

 duals of the same party at the same time, but in the same person 

 at different times ; how far referrible to the condition of the system, 

 and how far to atmospheric changes, is still uncertain. 



Respiration, and even continued muscular exertion, which neces- 

 sarily accelerates the breathing, are possible in very attenuated air, 

 as among the inhabitants of lofty regions ; but by any great and sud- 

 den change of density, whether of increase or diminution, this func- 

 tion becomes embarrassed. 



There is reason to believe that the quantity of oxygen absorbed 

 by the lungs does not always bear the same ratio to the quantity 

 received into their cells. At least, if the evolution of animal heat 

 is directly as the oxygen absorbed ; for on this supposition the air 

 at Chamoni having a density = 27, that on the summit of Mont 

 Blanc =17, and the temperature at the upper station being many 

 degrees below that at the lower, the absorption of oxygen must 

 have been, not relatively alone, but also absolutely greater, from 

 the rarer than from the denser air. 



The occurrence of haemorrhages in the ascent of high moun- 

 tains has been a frequent, but very variable phenomenon, and some 



