THE ELOOD. 491 



Volume of Carbonic Acid T> -nr -u^. 



produced in one hour. 



Horse . . . 21972 litres 13DO oz. 



Ox ... 27110 16-58 ' 



Sheep at 8 months 55-23 3*41 . 



Goat at 8 years . 21-48 1J 



Kid at 5 months . 11-60 f 



Pointer dog . 18-31 1J 



Dumas finds that a horse consumes 78 Jth ounces of carbon 

 per day, a dog a little over one ounce, and a cat a little over 

 half that quantity. The production of carbonic acid is 

 greater in early life than in adult animals. It is increased 

 by exercise, cold weather, during the act of digestion, and 

 during pregnancy. More carbonic acid is produced during 

 the day than at night, and though activity tends to this 

 result, if an animal is exhausted, the amount of carbonic 

 acid developed diminishes. 



Keynault has found that the smaller the animal the more 

 active the respiration, and in a great measure this is due to 

 the necessities of the small animal for the production of 

 animal heat. The whole of the oxygen which disappears 

 from the air during respiration does not form carbonic acid. 

 One part combines with hydrogen, sulphur, phosphorus, and 

 other substances. 



The blood absorbs oxygen, and discharges carbonic acid 

 and water. It thus undergoes the change from arterial to 

 venous blood. The oxygen penetrates through the respira- 

 tory mucous membrane and the coats of blood-vessels, to 

 become incorporated with the blood, which greedily absorbs 

 it. It was at one time supposed that the saline constituents 

 of blood became oxidized in the lung&, and were the special 

 carriers of oxygen, but the nitrogenous elements readily 

 appropriate it The changes occurring in the blood from 



