340 



Dr. W. Marcet. A Chemical Inquiry [June 20, 



I have made bo mention of the changes which occur in the urine 

 as the result of disease, for the reason that I purpose devoting a 

 special article to this subject, which is at present under investigation, 

 though necessarily slow in progress, and far from being completed. 



It is singular to observe that any important derangement of the 

 horse's health is associated with an acid urine, the presence of uric 

 acid and large phosphates, and the production of a clear human-like 

 urine in appearance ; this change is produced as soon as the animal 

 refuses food and commences to live on its own tissues. 



IX. "A Chemical Inquiry into the Phenomena of Human 

 Respiration." By William Marcet, M.D., F.R.S. Received 

 June 3, 1889. 



(Abstract.) 



Before entering upon this communication, I must beg to acknow- 

 ledge the valuable aid of my assistant, Mr. 0. F. Townsend, F.C.S., 

 to whose diligent, methodical, and careful work I am greatly indebted 

 for the results obtained in the present research. The numerous 

 calculations have all been made by both of us together, and the results 

 checked in every possible way to insure accuracy. 



My attention was first turned to the chemical phenomena of respira- 

 tion in 1875, and since then I have had the honour of communicating 

 to the Royal Society a succession of papers on the " Influence of 

 Altitude on Respiration," which have appeared in vols. 27, 28, 29, 

 and 31 of the ' Proceedings.' 



These inquiries show in a most conclusive manner that altitude 

 exerts an action on respiration depending entirely on the fall of 

 atmospheric pressure. The law can be expressed as follows : — The 

 volumes of air breathed, reduced to 0° C. and 760 mm., in order to 

 yield the oxygen necessary for the production of a given weight (say, 

 1 gram) of carbonic acid, are smaller on mountains under diminished 

 pressures than in the plains under higher pressures. 



My earliest experiments on the Breithorn, 4171 metres (13,685 feet) ; 

 the Col St. Theodule, 3322 metres (10,899 feet) ; the Riffel, 2368 

 metres (8428 feet) ; St. Bernard, 2473 metres (8115 feet) ; and the 

 Col du Geant, 8362 metres (11,030 feet), were all attended with a 

 fall of temperature on reaching into higher altitudes. This circum- 

 stance necessarily produced an increased combustion in the body, 

 to overcome the action of the cold, and introduced an element 

 in the inquiry not unlikely to interfere with the exclusive influence 

 altitude might exert on the chemical phenomena of respiration. 

 In order to overcome the present difliculty I spent three weeks 

 on the Peak of Teneriffe in the summer of 1878, where the 



