AIR. 



AIR. 



This theory has now ceased to "be acknow- 

 ledged ; and a common source of fallacious 

 reasoning lies in overlooking the fact, that 

 the air contains the germs of numerous or- 

 ganic forms, still capable of resuming their 

 active vitality when they meet with the 

 requisite conditions. Of this we have con- 

 vincing proof. For, if the liquid containing 

 the decomposing matters be heated to ebul- 

 lition for some time in a bottle or other 

 vessel, into the cork closing which two 

 bent tubes are inserted, and, after the air 

 has been completely displaced by thevapour, 

 the fresh air admitted be previously passed 

 through red-hot tubeSj or Pasteur's filter of 

 cotton-wool, organisms cease to be met with, 

 and the decomposition of the substance and 

 growth of the organisms no longer take 

 place, even in an indefinite period. That 

 the liquid in these cases does not experience 

 alteration rendering it incapable of sup- 

 porting the life of the animal forms intro- 

 duced, is shown by subsequently admitting 

 ordinary air, when the organisms appear as 

 rapidly as in fresh liquids. 



Vegetable forms are also constantly met 

 with as deposited from the air. In them, 

 the spores are probably alone the bodies by 

 means of which the diffusion of the lower 

 plants by the agency of the air is effected. 

 Minute fungi are frequently found, like the 

 animalcules above alluded to, in various 

 vegetable and animal liquids undergoing 

 fermentation and decomposition. The ques- 

 tion of the relation of these fungi to the 

 processes will be found discussed under 

 FERMENTATION and PUTREF ACTION ; and 

 the various genera and species found in dif- 

 ferent kinds of liquids are treated of under 

 the heads of these liquids. Fungi and algae 

 are also met with as parasites and ento- 

 phytes upon and in living animals : for an 

 account of these, see PARASITES. 



The lower forms of fungi are frequently 

 found growing upon surfaces from which 

 they can derive.no nourishment, as upon 

 slips of glass, window-panes, c. In these 

 cases they must derive their nourishment 

 from the atmosphere. When found in these 

 situations, however, they soon cease to grow 

 by subdivision of cells or gemmation, but 

 speedily form spores. The most common 

 ones in these situations are the sugar-fun- 

 gus- Penicillium glaucum and Aspergillus 

 penicillatus, Mucor, &c. 



The method of distinguishing whether 

 any minute particle deposited from the 

 air is of animal or vegetable nature, is de- 



scribed under TISSUES, ANIMAL and VE- 

 GETABLE. 



Organic bodies derived from the air are 

 sometimes met with in snow and hail. 

 See SNOW and HAIL. 



The air has frequently been examined in 

 regard to the presence of animal or vege- 

 table organisms, which might account for 

 the production of epidemic and infectious 

 diseases ; but the residts obtained in this 

 direction have not been very satisfactory. 

 Yet as, on adopting the principle of Pasteur's 

 filter, and the use of germicides in the 

 treatment of wounds, and in purifying the 

 air when infectious diseases prevail, most 

 decided benefit has been shown to result, 

 the further examination of the air may allow 

 of the detection in it of the germs of 

 disease which have probably been too often 

 passed over as mere granules, globules, &c. 

 of no import. The best plan of making 

 these experiments is to connect a glass tube, 

 twice bent at right angles, with an aspi- 

 rator : the free end of the tube should be 

 drawn to a fine point; and just above this 

 the tube should be blown into a bulb. The 

 point is then immersed in a small quantity 

 of pure water, and the water allowed to 

 run very slowly from the aspirator. The 

 water is then slowly drawn into the tube, 

 and the air is washed as it passes by the 

 water in the bulb. When a large quantity 

 of air has been washed by the water, the 

 latter is shaken briskly and allowed to run 

 into a clean glass for examination. 



Another method consists in closing, by 

 fusion, the end of a glass funnel, filling 

 this with ice, and collecting the drops of 

 water condensed from the air on its ouside, 

 in a receptacle placed beneath. See Micno- 

 ZYMES and SCHIZOMYCETES. 



Pouchet and Maddox have devised other 

 forms of apparatus for this purpose. 



The appearances presented by air as exist- 

 ing in cell-cavities is represented in PI. 47. 

 fig. 23 a, in the delicate cavities of a hair 

 in PL 29. fig. 1 ; and the lower part of the 

 same figure represents a portion from which 

 the air has been displaced by liquid. 



BIBL. Pasteur, Ann. d. Chim. 1862, p. 64, 

 & Sur les corpuscles organises de Tair, Ann. 

 d. Sc. Nat. (Zool] 1861, xvi. p. 26; Magnin, 

 Impaludisme, fyc., 1876; Robin, Micr. 1877, 

 p. 870; Miquel, Comptes Rendm, 1^79; 

 Cunningham, Mic. exam, of air, Calcutta ; 

 Tissandier, Poussieres de Vair ; Pouchet, 

 Aeroscopie, 1870 ; Tyndall, Lcct. Land. Inst. 

 (Times, Dec. 12, 1877), & Proc. Roy. Soc. 



