1815.J Dlsci3vefy of the Uses of the Cerehelluin. 423 



tisfied, and looks about for some more important function upon 

 which the great quantity of chyle absorbed may be expended. 

 Physiologists have traced the fond through the alimentary tube and 

 lacteal vessels into the subclavean vein ; the chyle having got fairly 

 into the circulation, is hurried, along with the blood and lymph 

 returning from all parts of the body, to the lungs. All the bloodv 

 and all the chyle, and all the lymph, must perform the pulmonary 

 circulation before they be admitted into tlie great systemic circula- 

 tion. Now let us attend to what takes place in the lungs. According 

 to your own calculation, as stated in the 737th page of the r)th vol. 

 of your System of Chemistry, od edit, there are thrown out of the 

 lungs by ordinary respiration in 24 hours no less than 40 000 cubic 

 inches of carbonic acid, a quantity which contains about 5. lb. 

 avoirdupois of solid carbon. Whence is this carbon derived ? The 

 food is the only source from whence such a supply of carbon can be 

 derived ; while the blood is at once the grand reservoir of carbon to 

 the lungs, and the venicle of vitality to the body. By this conjoint 

 view of respiration and nutrition, two mysteries are cleared up at 

 once — the source of the carbon, and the primary purpose of the 

 food. The life of man has often been poetically compared to the 

 burning of a fire, taper, &c. This poetical turns out a scientific 

 analogy. As long as there is a supply of fuel, and a iiee admission 

 of air, the animal fire continues lo burn; th« carbon of the fuel 

 combining with the oxygen of the atmosphere, and forming car- 

 bonic acid. Whenever the supply of fuel, or of atmospheric air, is 

 interrupted, the fire declines; if the interruption is mcmentarv, the 

 fuel may rekindle ; if the interruption has been too long, the fire 

 goes out for ever. Thus we sec tliat respiration is the great primary 

 function for whose sake digestion was instituted ; while all the ex- 

 cretions, like the ash-pits of a furnace, are things of mcrelv 

 ^condary moment in the animal economy. To ensure a supply tt> 

 respiration, carbon has been made the great substratum of vegetable 

 and animal fabric — the chemical skeleton ; so that when chyle is 

 deficient, the very substance of the body is carried off to the lungs, 

 and sacrificed on the shrine of respiration. No living organized 

 body, from the primitive germ up to the adult stature, from the 

 microscopic animalcule up to the whale, from the rudest lichen Up 

 to man, has ever been ^een without organs of respiration. The 

 cotyledons of vegetable seed must emit carbonic acid gas ert the 

 radicle begins to send down its fibres into the earth ; and if these 

 cotyledons ceabC their respiration, and fail to become seminal leaves 

 before the ])lumula rises and spreads its foliage to the lieavcn«, the 

 plant dies. If tiie pores of a fecund egg are stopped up, tlie lien 

 may hatch upon it while she has heat in her body without brin{ring 

 forth the chiik. Nor does the chick, afi'-r it is fully formed, delav 

 a moment to drive its bill through the shell for the free admission of 

 air. The embryo, ere it begins to evolve, is connected to the uterus 

 by means of a pbuenta as an intermediate agent between the foetus 

 and tlie maternal lungs ; and whenever the function of th^ placenta 



