ON THE FUNCTIONS OF LIFE. > 



essential to the former than the latter, in propor- 

 tion to the greater amount of oxygen which they 

 require. 



The symptoms that follow the inhalation of 

 these gases in small quantities, or in a state of 

 mechanical mixture with the atmosphere, are 

 diminished respiration, attended with chilliness, 

 imperfect arterialization of the blood, which is 

 sent to the brain, stomach, and other organs, of a 

 dark hue, as shown by the pallid or purple colour 

 of the skin. Under such circumstances the pulse 

 becomes low and feeble, while all the energies of 

 life are reduced, for the same reason that they are 

 diminished by loss of blood, breathing a rarefied 

 atmosphere, or by depriving the system of caloric 

 more rapidly than it is supplied by respiration. 

 And it is worthy of special notice, that as the brain 

 is supplied with a much larger proportion of blood 

 than an equal weight of any other organ, it is 

 sooner affected by loss of blood, or by whatever 

 impairs its vital properties, than any other part of 

 the system, for the same reason that birds are 

 more seriously affected by impure air than mam- 

 malia, and the latter than cold blooded animals. 

 For example, we have seen that in birds the cir- 

 culation is so rapid, that all the blood in the system 

 passes throughout the different tissues, in some- 

 thing less than a minute, during which it gives 

 out to the solids whatever amount of caloric it 

 receives in the lungs, and thus returns to the 

 state of venous blood, which, if not again properly 



