AIR. 



[ 24 ] 



AIR. 



This theory lias now ceased to he aclinow- 

 ledgecl : aud 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 the vapour, 

 the fresh air admitted be previously passed 

 through red-hot tubes, 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 diifusion of the lower 

 plants by the agency of the air is efit?cted. 

 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 

 Feemektation and I'i'teefaction ; and 

 the various genera and species found in dif- 

 ferent kinds of liquids are treated of mider 

 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 atmospliere. When found in these 

 situations, however, they soon cease to gxow 

 by subdivision of cells or gemmation, but 

 speedily form spores. The most common 

 ones in these situations are the sugar-fun- 

 gus — Penicillivin glaticum and Asjiergilhis 

 peniciUatus, Miicor, &c. 



The method of distinguishing whether 

 any minute particle deposited from the 

 air is of animal or vegetable natme, is de- 



scribed under Tissues, Animal and Ve- 

 getable. 



Organic bodies derived from the air are 

 sometimes met with in snow and hail. 

 See S^'ow and Hail. 



The air has frequently been examined in 

 regard to the presence of animal or vege- 

 table organisms, which might accoimt for 

 the production of epidemic and infectious 

 diseases ; but the results 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 pm-ifying 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 tine point; aud just above this 

 the tube should be blown into a bidb. 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 b'riskh- 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 Avith ice, and collecting the drops of 

 water condensed from the air on its ouside, 

 in a receptacle placed beneath. See Miceo- 

 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 «, in the delicate cavities of a hair 

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

 same figure represents a portion from which 

 the air has been displaced bv liquid. 



BiBL. Pasteur, Ami. d. Chim. 18G2, p.64, 

 & Siir les corpuscles organises de Voir, Ann. 

 d. Sc. Not. (Zool.) 1801, xvi. p. 26; Magnin, 

 Impabtdisyne, ^-c, 187G; Robin, Micr. 1877, 

 p. ^70; Miquel, Comptcs Jx'cndus, 1,^79; 

 Cunningham, Mic. e.vcnn. of air, Ca/cidta ; 

 Tissandier, Poiissicres de rair ; Pouchet, 

 Aeroscopie, 1870 ; Tvndall, Led. Lond. Inst. 

 (Times, Dec. 12, 1877), k I'roc. Hoi/. Sue. 



