68 THE NATURE AND" TREATMENT OF 



Having briefly alluded to the use and properties of oxyge^. 

 nitrogen next engages our attention. 



Nitrogen. — This gas possesses all the physical properties 

 of common air. It is distinguished for its repugnance to enter 

 into chemical combinations. Its principal use seems to be, to 

 neutralize the effect which might result from the action of 

 pure oxygen on the animal tissues. It is a non-supporter of 

 vitality, yet there appears to be a continual absorption of it by 

 the blood. In fact, the blood, and all the organized tissues 

 contain about 17 per cent of nitrogen. 



Carbonic Acid Gas. — This gas is supposed to possess 

 greater density than common air, and therefore is generally 

 found to occupy a space next the earth, or floors of un venti- 

 lated stables and dwelling houses, or such situations as contain 

 the materials, which generate it by decomposition. The miners 

 have given it the name of " choke damp." It is often present 

 in the stomach and intestines of animals, generated by putre- 

 faction, and often causes death by distension. It is an invisi- 

 ble fluid, of pungent odor. 



Some persons are disposed to believe that carbonic acid gas 

 is so dense as to occupy no other space than beneath the com- 

 mon atmosphere, in close proximity with the earth, and floors 

 of cellars and stables. This is not the case, for it has been 

 discovered at the greatest heights which the industry of man 

 has been able to penetrate. Saussure found this gas at the 

 summit of Mount Blanc, a point of the earth mantled with 

 perpetual snow ; and Ilumbolt has recently demonstrated the 

 presence of this gas, in air brought by M. Garnerin, from a 

 height not less than 4,280 feH3t above the earth's surface, to 

 which height he had arisen in an air balloon. From these 

 facts we are led to infer that, notwithstanding the current 

 opinion regarding the great density of carbonic acid gas and 

 tlie aflinity that seems to exist between it and the earth's sur- 

 face, it must enter into combination with the atmosphere, there- 

 fore is chemically combined, or artificially mixed, with the 

 same. The following anecdote settles the point : — 



Not long ago the king of Naples had a very fine elephant 



