September 1, 1896.] 



KNOWLEDGE. 



201 



length of time. Deal boxes split with the heat and dryness, 

 as did the boots of the two members of the expedition, the 

 soles coming away from the uppers, so that the party 

 returned to the seaside in a somewhat dilapidated condition. 

 From the highest station at Alta Vista (ten thousand seven 

 hundred feet) two expeditions were made to the cone and 

 summit itself, but the sulphurous vapours given off pre- 

 vented any determination of carbonic acid being made on 

 the summit. 



The results of the experiments at Teneriffe showed, as 

 had been anticipated, that there was no increase in the 

 carbonic acid given oil' from the lungs 

 between the seaside and the summit of 

 the Peak ; so that the increase found in 

 Switzerland on the Col St. Theodule, the 

 Breithorn, etc., must have been due to 

 cold and not to altitude. In addition it 

 was noticed, as had been the case in the 

 Alps, that the actual volume of air 

 breathed, reduced to normal temperature 

 and pressure, was less than at the seaside. 



Experiments were made on the amount 

 of water exhaled from the lungs at the 

 seaside and at the three stations on the 

 Peak. The results showed most distinctly 

 that the less the atmospheric pressure the 

 greater the amount of water given off. 

 This might have been expected, as a 

 decrease in pressure is known to facilitate 

 evaporation. In the winter of 1888-9, 

 Dr. Marcet continued his inquiry into the 

 subject of respiration. Instead of collecting 

 the air expired from the lungs in bags, as 

 had been done in the mountains, bell- 

 jars were used in this latter work, which 

 was carried out in the Physiological 

 Laboratory at University College, London. 

 These bell-jars held forty litres, and were 

 so beautifully balanced that it was im- 

 possible for the person under experiment 

 to tell whether he was breathing into them 

 or into the open air. With the use of 

 these bell-jars Dr. Marcet undertook an 

 inquiry into the subject of re-breathed 

 air. One of the bell-jars was filled with 

 thirty- five litres of air, and the person 

 under experiment breathed both into and 

 out of this vessel for five minutes. At the 

 end of this period, by merely altering the 

 connections he was enabled to breathe 

 with fresh air. The air coming from his 

 lungs was conveyed to a second bell-jar, 

 previously emptied. The conclusions 

 derived from this work are interesting. 

 A large proportion of the carbonic acid 

 produced remains stored up in the blood, 

 so that when fresh air is taken into the 

 lungs large volumes of air are breathed, 

 because of the desire to get rid of the excess of carbonic 

 acid. All efl'ects of re-breathing pass away in about six 

 minutes when fresh air is turned on. 



Kegnault and Keiset were the first to observe that all 

 the oxygen absorbed in the lungs was not returned as 

 carbonic acid, a fact that has been confirmed by all later 

 observers. Dr. Marcet found that this "occluded oxygen" 

 was greatest in the hour that follows a meal, falling oS', 

 apparently, after that period ; but the changes in this 

 absorption of oxygen are so great that it is difficult to 

 follow them at all closely. This oxygen is used obviously 



in tissue changes apart from mere combustion. We do not 

 know by what process carbonic acid is generated in the 

 body, but, according to Hermann, there is no single 

 instance of direct oxidation in the chemical phenomena of 

 life. 



After completing this chemical work by the aid of an 

 ingenious burette he had constructed for the purpose, Dr. 

 Marcet undertook an investigation into the different forms 

 of human respiration. Beginning with normal breathing 

 in a state of repose, experiments were made on forced 

 or laboured breathing, respiration under exercise, and 



A A Normal 



BC Farced. CD After Stage 



EF Stepping 66 times per minute, FG After Sta^c 



respiration as controlled by the mental exercise of the 

 will. In order to obtain records of these different con- 

 ditions of breathing, an apparatus was employed to trace 

 the actual movements of the lungs. I'or this purpose a 

 glass pen, charged with ink, was fixed to the end of 

 a rod attached to the bell-jar. The point of the pen 

 pressed against a ruled chart stretched on a 

 made to revolve horizontally at 

 work. The horizontal lines on 

 number of litres of air expired, 

 the time in minutes. When breathing commenced the 



drum, 

 a given rate by clock- 

 the charts showed the 

 and the vertical lines 



