CONSUMPTION OF OXYGEN. 143 



oxygen, in the warm-blooded animals and in the human subject, have noted a marked in- 

 crease at low temperatures. Immediately after birth, the consumption of oxygen in the 

 warm-blooded animals is relatively very slight. Buffon and Legallois have shown that, 

 just after birth, dogs and other animals will live for half an hour or more under water ; and 

 cases are on record where life has been restored in newly-born children after seven, and, 

 it has been stated, after twenty-three hours of asphyxia. (Milne-Edwards.) During the 

 first periods of existence, the condition of the newly-born approximates to that of a cold- 

 blooded animal. The lungs are relatively very small, and it is some time before they fully 

 assume their function. The muscular movements are hardly more*than is necessary to take 

 the small amount of nourishment consumed at that period, and nearly all of the time is 

 passed in sleep. There is also very little power of resistance to low temperature. Although 

 accurate researches regarding the comparative quantities of oxygen in the venous and 

 arterial blood of the foetus are wanting, it has been frequently observed that the differ- 

 ence in color is not so marked as it is after pulmonory respiration becomes established. 

 The direct researches of "W. F. Edwards have shown that the absolute consumption of 

 oxygen by very young animals is very small ; and the observations of Legallois on rabbits, 

 made every, five days during the first month of existence, show a rapidly-increasing de- 

 mand for this principle with age. 



Eegnault and Reiset have shown that the consumption of oxygen is greater in lean 

 than in very fat animals, provided they be in perfect health. They have also shown that 

 the consumption is much greater in carnivorous than in herbivorous animals ; and, in ani- 

 mals of different sizes, it is relatively much greater in those which are very small. In 

 small birds, such as the sparrow, the relative quantity of oxygen absorbed was ten 

 times greater than in the fowl. 



During sleep the quantity of oxygen consumed is considerably diminished ; and in hi- 

 bernation it is so small, that Spallanzani could not detect any difference in the composi- 

 tion of the air in which a marmot, in a state of torpor, had remained for three hours. 

 In experiments on a marmot in hibernation, Regnault and Reiset observed a reduction 

 in the quantity of oxygen consumed to about $ of the normal standard. 



It has been shown by experiments, that the consumption of oxygen bears a pretty 

 constant ratio to the production of carbonic acid ; and, as the observations upon the influ- 

 ence of sex, number of respiratory acts, etc., on the activity of the respiratory processes, 

 have been made chiefly with reference to the carbonic acid exhaled, we shall consider 

 these influences in connection with the products of respiration. 



Experiments on the effect of increasing the proportion of oxygen in the air have led 

 to varied results in the hands of different observers. Regnault and Reiset, whose 

 observations on this point are generally accepted, did not discover any increase in the 

 consumption of oxygen when this gas was largely in excess in the atmosphere. 



The results of confining an animal in an atmosphere composed of twenty-one parts of 

 oxygen and seventy-nine parts of hydrogen are very curious and instructive. When 

 hydrogen is thus substituted for the nitrogen of the air, the consumption of oxygen is 

 largely increased. Regnault and Reiset attribute this to the superior refrigerating power 

 of the hydrogen ; but a more rational explanation would seem to be in its superior 

 diffusibility. Hydrogen is the most diffusible of all gases ; and, when introduced into the 

 lungs in place of the nitrogen of the air, the vitiated air, charged with carbonic acid, 

 is undoubtedly more readily removed from the deep portions of the lungs, giving place 

 to the mixture of hydrogen and oxygen. It is probably for this reason that the 

 quantity of oxygen consumed is increased. It is probable that the nitrogen of the air 

 plays an important part in the phenomena of respiration by virtue of its degree of 

 diffusibility. 



In view of the great variations in the consumption of oxygen dependent on different 

 physiological conditions, such as digestion, exercise, temperature, etc., it is impossible to 

 fix upon any number which will represent, even approximatively, the average quantity 



