354 



RESPIRATION. 



only of the absolute quantity of carbon which 

 escapes from the body in the form of carbonic 

 acid gas in the different classes of animals, but 

 also the relative proportion of this to the 

 weight of the body, is a matter of considerable 

 physiological interest, especially with refer- 

 ence to the source of animal caloric. From 

 the experiments of Scharling, Andral, and 

 Gavarret, it is evident that the young of the 

 human species relative to their weight consume 

 considerably more oxygen gas, and evolve 

 more carbonic acid gas by respiration, than the 

 middle-aged ; and that the latter again evolve 

 more carbonic acid than those far advanced 

 into old age. Valentin and Brunner have 

 calculated, from experiments performed on 

 Valentin, who at the time was 33 years of age, 

 that for every gramme weight (15'433 Troy 

 grains) of his body, there was evolved '0089 

 Troy grain of carbonic acid gas, containing 

 0024 Troy grain of carbon ; and this calcu- 

 lation approximates pretty closely to one 

 based upon the results of Andral and Gavarret 

 upon the evolution of carbon, combined with 

 those of Qnetelet upon the average weight of 

 the body at this period of life. * The follow- 

 ing table, calculated from the experiments of 

 different observers, to show the quantity of 

 carbon consumed in the 24 hours for every 

 100 grammes weight (1543'3 Troy grains) of 

 the body in the four divisions of the verte- 

 brata, is given by Vierordt : 



Troy Grains. 

 Tench (Provencal and Humboldt) -370 1 



Frog (Marchand) 1-342= 4 



Man (Scharling) 4'506 = 12 



Pigeon (Boussingault) 42'317 = 114 



Quantity of oxygen absorbed at the lungs. 

 That a quantity of oxygen gas greater than 

 what is necessary to form the carbonic acid 

 gas in the expired air disappears from the 

 inspired air, is now placed beyond a doubt. 

 The quantity of oxygen gas that disappears 

 from the inspired air by absorption at the 

 lungs is not uniform, even in the same indi- 

 vidual, for any length of time, and the varia- 

 tions in this respect are in all probability 

 determined by the same circumstances which 

 affect the evolution of carbonic acid gas, the 

 absorption of oxygen being increased when 

 the evolution of carbonic acid is increased, 

 and vice versa. Dalton calculated that he 

 himself respired 500 cubic feet of atmospheric 

 air, containing 105 cubic feet of oxygen, in 

 the 24 hours, and that 25 cubic feet of the 

 oxygen, weighing 15,120 grains, or 2'6 Ibs. 

 Troy, were absorbed at the lungs. Valentin 

 and Brunner, in 34 analyses of the air expired 



the quantity of carbonic acid evolved in respiration 

 in different classes of animals up to the period when 

 the work was published, are thrown into a tabular 

 form in Burdach's Physiologic, 2nd edition, trans- 

 lated by Jourdan, torn. ix. p. 512. 



* A table constructed on these data, exhibiting 

 the probable quantity of carbon which combines with 

 oxygen to form the carbonic acid gas evolved at 

 the lungs at different ages in the human species, is 

 given at p. 569 of Valentin's Lehrbuch. 



by 3 individuals between 33 and 54 years of 

 age, found the average quantity of 0x3 gen gas 

 to be 16'033, the maximum 17*246, and the 

 minimum 14*968 parts by volume in the 100 

 parts of the expired air. Proceeding on these 

 results of Valentin and Brunner, we may esti- 

 mate the average amount of oxygen that dis- 

 appears from the inspired air at 4'78 by 

 volume in the 100 parts. 



While the experiments upon the relation of 

 the quantity of oxygen absorbed at the lungs 

 to that of the carbonic acid gas evolved, made 

 by Lavoisier, Sir H. Davy, and Dalton on the 

 human species, by Legallois, Dulong, Despretz, 

 and Dr.W. F. Edwards upon the warm-blooded 

 animals, by Treviranus upon several cold- 

 blooded animals, and by Marchand upon frogs, 

 all concur in making the oxygen absorbed 

 greater than what is necessary to form the 

 carbonic acid exhaled, they exhibit very con- 

 siderable differences in the relative propor- 

 tions of the absorbed oxygen and exhaled 

 carbonic acid gas. In some of these experi- 

 ments, the oxygen absorbed was considerably 

 greater than what is necessary to form the 

 carbonic acid gas. In Marchand's experiments 

 on frogs subjected to prolonged fasting, the 

 relation of the oxygen absorbed to the car- 

 bonic acid evolved constantly increased, until 

 it amounted to between 410430 : 100.* 

 Valentin and Brunner, in their experiments 

 on the human species, found the relative 

 proportions of these two gases to approximate 

 so closely to their diffusive volumes, that they 

 believed the small difference between the 

 results obtained by actual experiment and 

 when calculated according to the law of the 

 diffusion of gas, discovered by Graham, arose 

 from incidental circumstances ; and as the 

 diffusive volume of carbonic acid gas is to 

 oxygen gas as 1 : 1-1742, they maintain that 

 for every 1 volume of carbonic acid gas 

 evolved from the blood, 1-1742 volume of 

 oxygen gas is absorbed. Valentin has given 

 the following table, constructed from facts 

 furnished by Quetelet, Andral, and Gavarret, 

 conjoined with calculations of the relative 

 quantities of oxygen absorbed and carbonic 

 acid evolved according to the law of the 

 diffusion of gases, to exhibit the weight of the 

 body, the quantity of carbon consumed in 

 respiration, and the probable amount of oxy- 

 gen absorbed and carbon consumed at the 

 different periods of life in the human spe- 

 cies f : 



* At page 563 of Valentin's Lehrbuch are two 

 tables exhibiting the relative proportions of oxygen 

 gas absorbed and carbonic acid evolved, as ascer- 

 tained by direct experiment, and as calculated ac- 

 cording to the law of the diffusion of gases. AVe 

 shall have occasion to make some remarks on this 

 subject when we come to discuss the theory of respi- 

 ration. 



f Opus cit. p. 571. The weights and measures in 

 the original table are here reduced to Troy weight 

 and English cubic inches. 



