Miscellanies. 367 



39. Products of Respiration at different periods of the day ; by Chas. 

 T. CoATHuPE, Esq. — Lon. and Edin. Phil. Mag., June, 1839. 



The subject of the experiments was 38 years old, stature 5 feet 8 inches, 

 weight 140 pounds; average pulse 60 to 63 per minute ; average inspira- 

 tion 18 to 21 per minute. 



Omitting the description of apparatus, and the details of experiment ; 

 some of the most important results are as follows : 



The corrected result of 32 experiments made before breakfast and 

 comprising 8 days, gave 4.37 for the per centage of carbonic acid pro- 

 duced in respiration. 



Fifteen experiments between 10 and noon in 7 days indicated 3.90 per 

 cent, of carbonic acid. 



Seven experiments between noon and 1 P. M. in five days gave 3.92 

 per cent. 



Twenty nine experiments between 2 P. M. and 5^ P. M. in 8 days, 

 indicated 4.17 per cent. 



Seventeen experiments between 7 P. M. and 8J P. M. in 8 days, gave 

 3.63 per cent. 



Twenty four experiments between 9 P. M. and midnight indicated 4.12 

 per cent, and the average of all the experiments, 124 in number, in almost 

 every hour between 8 A. M. and midnight in eight days, gives 4.09 per 

 cent, as the total daily average of the carbonic acid gas in the air re- 

 spired from the lungs. 



The carbonic acid gas produced in respiration, is therefore, a variable 

 quantity — less during active digestion and increasing with abstinence 

 from food; in the same individual, it varies at similar periods of different 

 days. Excitement of any kind, whether from stimulus or annoyance, 

 caused a diminution of carbonic acid in the air respired, compared with 

 the ordinary average of that respired at a similar period of the day, and 

 during a state of ordinary tranquillity. While the total average indicated 

 4.09 the maximum observed at any single examination was 7.98. This 

 was at 8 A. M., Feb. 5, the maximum was 1.91 ; at 7^ P. M., Feb. 

 7th. These results differ widely from those of Messrs. Allen and Popys, 

 published in Phil. Trans, in 1809. Their average was 3 per cent, of 

 carbonic acid in the air respired. By protracting the respiratory process, 

 there was an increase of carbonic acid of one fourth more than the av- 

 erage of natural respiration. Due allowance being made for this and 

 for aqueous vapor, the 8 per cent, of Allen and Popys is reduced to 6.4 

 per cent. Their experiments were made before breakfast and just be- 

 fore dinner when the largest quantity of carbonic acid is produced ; the 

 considerable volumes of air which they employed were renewed not over 

 thrice, and were obtained at one period of the day ; the quantity of car- 

 bonic acid which they found, had it been obtained in natural respiration, 

 would not have been over 6.4 per cent., which is the maximum at the 

 most favorable periods for its production. 



