292 ANNUAL OF SCIENTIFIC DISCOVERY. 



EXCRETION OF CARBONIC ACID AND ABSORPTION OF OXYGEN. 



Pettenkofer and Voit have presented to the Academy of Munich 

 a communication on the difference of the excretion, in the human 

 subject, of carbonic acid and absorption of oxygen by day and 

 night, during rest and labor. The new arrangement of their 

 great respiratory apparatus easily admits of a division of 24 hours' 

 investigation into two periods. 



The subject for observation, a sound, strong watchmaker, 28 

 years of age, and of 60 kilogrammes weight, entered the appara- 

 tus July 31, at 6 A. M., and remained in it till August 1, 6 A. M. 

 The time from 6 a. m. till 6 p. m. is understood to be day, the rest 

 night. The man took, at his regular meal hours, medium quantities 

 of his usual food whose elementary composition had been carefully 

 made out. He occupied himself in reading and in cleaning a lit- 

 tle watch ; he went to bed at 8 P. M., and slept well until 5 A. M. 

 His condition was perfectly normal during the investigation. 



The excretion of carbonic acid amounted, during daytime, to 

 58 per cent., during night to 42 per cent. ; the absorption of ox}'- 

 gen during daytime to onl}' 33 per cent., during night to 67 per 

 cent. The excretion of urea, as has been known heretofore, is 

 always greater during day than during night. 



On the day of rest, the excretion of urea, in both daily periods, 

 was in exact proportion to the excretion of carbonic acid ; there 

 was excreted of both 58 per cent, during day and 42 per cent, 

 during night. Most surprising is the antagonism in the excretion 

 of carlDonic acid and the absorption of oxygen between the two 

 daily periods, even with all possible avoidance of muscular exer- 

 tion, on July 31. This shows that mere waking, and the impres- 

 sions experienced by the senses in that state, have an influence on 

 the consumption of material serving to produce the processes of 

 life. 



This antagonism is still greater when the davof labor is included 



Oct •^ 



in the comparison ; the excretion of carbonic acid and the ab- 

 sorption of oxygen b}' day and night are then in exactly inverse 

 proportion. The carbonic acid was excreted at the rate of 69 per 

 cent, during day, 31 per cent, during night; the oxygen absorbed 

 at the rate of 31 per cent, during day, 69 per cent, during 

 night. 



For daytime, while awake, we therefore produce a great deal 

 of carbonic acid at the expense of the oxygen absorbed during 

 rest and sleep. The will finds the material prepared for its spon- 

 taneous movements. 



So much oxygen as is used up in excess during one day, so 

 much is taken up for compensation during the following night, 

 and as long as this takes place the body is prepared in the morn- 

 ing for new labor. In compiring. the total of the two days of 

 experiment, it appears that, on the day of labor, there were 373 

 grammes of carbonic acid more excreted than on the day of rest, 

 and 246 grammes of oxygen more absorbed ; — 373 grammes of 

 carbonic acid containing 271 grammes of oxygen, there is only a 



