RESPIRATION. 



LESSON IV. 



FUNCTIONS OP NUTRITION Respiration Necessity of contact 

 with tin- ui.r rfspk$xiti Composition of the atmosphere I J riii' 

 cipnl phenomena of respiration the Luiiys Mechanism of m-- 

 piration Animal Heat. 



OF RESPIRATION. 



We have already seen that the. arterial blood, by its action 

 upon the living tissues, loses those qualities which make it fit for 

 the support of animal life, and after having been in this way 

 vitiated, it regains its first properties by contact with the air. 



1. Tne. transformation of venotts into arterial titooa, by I he 

 action of the <viY, constitutes the phenomenon of RESPIRATION. 



2. Respiration, and consequently contact w r ith the air, is in- 

 dispensable to all living beings; plants as well as animals feel the 

 want of it, and when deprived of it, both very soon perish. 



3 When, from any cause whatever, respiration is arrested, all 

 the animal functions are disturbed. Life soon ceases to be mani- 

 fest ; the animal falls into a state of asphyxia or apparent death, 

 and in a very short time life becomes entirely extinct. 



4. At first sight, we might believe that animals which live in 

 the depths of the waters, as fishes, are removed from the influence 

 of the air, and consequently form an exception to the law of which 

 we have spoken; but it is not so, for the liquid in which they 

 dwell, absorbs and holds in solution a certain quantity of air 

 which may be easily separated from it, and which is sufficient for 

 the support of life in them ; it is impossible for them to exist in 

 water deprived of its air, and they are seen to become asphyxia- 

 ted, and die, just as the niamfniferae and birds do, when excluded 

 from the action of the atmospheric air under its ordinary form. 



5. In man and in the other mammalia the apparatus of respira- 

 tion consists: 



1 st. Of the lungs, organs which are the seat of this function ; 



2nd. Of canals, by which the air from without is conveyed in- 

 to the lungs ; 



3rd. Of organs which effect the entrance of the air into this 

 apparatus, and which afterwards expel it, co make room for fresh 

 supplies of this fluid. 



1. What constitutes the phenomenon of respiration ? 



2. Is contact wuh the air nece>sary to all living beings f 



3. If respiration be arrested what is the consequence ? 



4. Do fish requi e contact with the air ? 



5. What parts compose the apparatus of respiration ? 



F 



