390 OF RESPIRATION. 



occasions fasted for more than twenty-four hours, and collected all the Car- 

 bonic acid exhaled during the whole period, or during ten minutes at each hour 

 of the waking day. He found the total daily amount of carbon exhaled at 

 rest and whilst fasting to be 5.923 oz. ; and there was scarcely any variation 

 in the hourly quantity during the hours of the day. He noticed that there 

 was a line below which the quantity of Carbonic acid did not fall, dui'iug 

 waking hours in health ; this, which he has termed the basal line, is that 

 observed at rest and in the absence of food. The increase above that line, 

 which is caused by food, seldom exceeds one half of the basal quantity, or 

 about 3 grains per minute. He has shown that the increase is from 2 to 3 

 grains per minute after breakfast and tea, and from 1 to 2 grains per minute 

 after early dinner, whilst he scarcely found any increase after supper. He 

 has examined the influence of numerous foods, as flesh, fish, albumen, 

 gelatin, bread, rice, oatmeal, cane, grape, and milk sugar, milk, tea, coffee, 

 cocoa, starch, gluten, butter, olive oil, alcohol, rum, gin, brandy, sherry, and 

 port wine, beer and spirits. All nitrogenous foods gluten, casein, flesh, fish, 

 albumen, and gelatin increased the evolution of Carbonic acid to the extent 

 of f to 1 grain per minute; but tea, coffee, bread, rice, oatmeal, milk, and 

 sugar increased it from 1 to 3 grains per minute. Fats and starch did not 

 increase it; alcohol, rum, and ales increased it from 2 a grain to 2 grains 

 per minute, whilst brandy and gin decreased it, and 3 ounces of wine exerted 

 but little influence. The inhalation of the aroma of wines decreased it. 

 All Dr. Smith's experiments were made in the sitting posture, at rest, before 

 breakfast, and upon one substance alone in moderate quantity, the dose of 

 which was repeated every ten or fifteen minutes, until the maximum influ- 

 ence had been obtained. With sugar, alcoholic liquids, tea, coffee, the max- 

 imum influence was observed in from twenty to thirty minutes; but with 

 bread, oatmeal, milk, and flesh, it was commonly later, and continued from 

 Is to 2a hours. With sugar and tea there was frequently an increase of 1 

 grain per minute in less than ten minutes. The whole of the Carbonic acid 

 exhaled during five minutes at a time for two hours was collected and weighed ; 

 the percentage was not sought for. Dr. Smith has called attention to the 

 separate action of the alcohol, aromas, sugars, and nitrogenous matters in 

 each of the alcoholic compounds. Similar though less extended and perfect 

 observations have been made by Vierordt, Bidder, Schmidt, and Perrin, 1 

 and others, which generally corroborate the conclusions drawn by Dr. E. 

 Smith. 



Vii. Muscular Exertion or Repose. The effect of bodily exercise, in mod- 

 eration, is to produce a considerable increase in the amount of Carbonic acid 

 exhaled, both during its continuance, and for some little time subsequently 

 to its cessation. According to the observations of Vierordt, the increase 

 amounts to one-third of the quantity exhaled during rest, and it lasts for 

 more than an hour afterwards; being manifested in the greater quantity of 

 air respired, and in the larger percentage of Carbonic contained in it. If 

 the exercise be prolonged, however, so as to occasion fatigue, it is succeeded 

 by a diminished exhalation. Dr. Ed. Smith found that whilst walking at 

 two and three miles per hour, the quantity of Carbonic acid evolved was 

 18.1 grains and 25.83 grains per minute, which are respectively 1.85 and 

 2.64 times more than that eliminated iu the quiet sitting posture. With 

 treadwheel labor the quantity varied from 42.9 grains to 48.66 grains. After 

 the exertion had ceased, the increase continued for some time; and not the 

 least exertion could be made, even when sitting, without disturbing the 

 results. In the experiments of Petteukofer and Voit 2 the following results 



Rcndus, 1864, p. 257. 2 Miinohener Akad. Berichte, 1867, No. 10. 



