GERM THEORY AND SPONTANEOUS GENERATION. 



389 



phenomenon, when a spirit lamp was set be- 

 low a cylindrical beam in his laboratory, of a 

 cloud blacker than smoke arising through the 

 beam, which was at first suspected to be the 

 carbon liberated by the flame, but which, on 

 experimenting with a red-hot iron and with a 

 hydrogen flame, he discovered was not smoke ; 

 he concluded therefore that it was due to the 

 complete consumption of the floating dust in 

 the upward passage of the heat, which left the 

 air free of the matter which reflects and dif- 

 fuses the light. The same phenomenon is seen 

 when a corked flask which has been allowed to 

 stand a couple of days is traversed by a con- 

 centrated beam of light : the beam is broken 

 when encountering the still air of the flask 

 after the floating matter has attached itself to 

 the sides, and passes through it as through a 

 vacuum, reappearing on the other side of the 

 glass. Acting on the knowledge that the air 

 which is kept perfectly still will clear itself of 

 the floating particles which he supposed to be, 

 in part at least, the germs of fermentation, 

 Tyndall constructed a wooden case with a glass 

 front and windows, with air-tight test-tubes 

 passing through its bottom, with their open 

 ends extending for one fifth of their length 

 into the chamber. A connection is established 

 with the outer air by long winding pipes in 

 which the floating matter will be detained 

 while the air passes through. An aperture 

 above is closed with India-rubber, through a 

 pinhole in which a long fine pipe is inserted ; the 

 aperture is further guarded by a stuffing-box 

 filled with cotton soaked with glycerine, to 

 prevent the entrance of any particles through 

 the movements of the pipette. The inner sides 

 of the case are coated with glycerine to detain 

 the dust after it settles. After leaving the 

 chamber for two or three days for the dust to 

 settle, and finding the air clear by the test of 

 a beam of light thrown through its windows, 

 Tyndall pours putrescible infusions into the 

 glass tubes through the pipette, which has a 

 funnel at its upper end, and boils the liquid to 

 kill the germs contained in it by applying a 

 bath of heated oil to the lower closed ends of 

 the test-tubes, which protrude below the bot- 

 tom of the case. Tyndall tested in 1875 and 

 1876 a great variety of putrescible liquids, 

 including liquid excretions and infusions of 

 all parts of domestic animals, game, fish, and 

 vegetables, in more than fifty such quiet cham- 

 bers, each containing some half a dozen test- 

 tubes. In every instance the liquid in the 

 chamber remained clear and sweet, in some 

 cases for more than a twelvemonth, while the 

 same infusion tested at the same time in the 

 outside air rapidly putrefied. After the liquids 

 had remained, pure and limpid in the stilled 

 chambers for three months, he opened some of 

 them, and found that it required but three 

 days for them to swarm with living creatures. 

 Tyndall tested about 500 organic liquids and 

 infusions in such moteless chambers, with- 

 out obtaining life in a single instance. His ex- 



periments in hermetically sealed flasks, in which 

 the heterogenists asserted that life had repeat- 

 edly shown itself after sterilizing the liquids 

 by boiling, were still more numerous, amount- 

 ing to 940 : in these cases he closely followed 

 the conditions prescribed by Dr. Bastian, and 

 under which spontaneous generation was al- 

 leged to have taken place. On the assertion 

 that a higher temperature than had been be- 

 fore supposed was more conducive to the gen- 

 eration of life in air-tight flasks, he exposed 

 his for nine days to a temperature varying 

 from 101 to 112 F., from two to six days be- 

 ing the limit required for generation according 

 to the heterogeuists ; he then placed them for 

 fourteen days in a temperature of about 115, 

 the thermometer rising on some occasions to 

 118 and 119. 



The solutions were obtained by soaking 

 sliced vegetables and other organic substances 

 in distilled water kept at a temperature of 

 120 for four or five hours. The liquor was 

 then poured off, boiled, and filtered, the in- 

 fusion being then as clear as drinking water, 

 and of a specific gravity of 1*006 or greater. 

 The flasks were small narrow-necked bulbs of 

 glass, and could be hermetically closed by 

 melting the glass of the neck in a flame and 

 drawing it out to a point. They were filled by 

 first dipping their mouths, after heating them, 

 into the liquid, and then chilling them, a por- 

 tion of the liquid ascending into the flask on 

 the contraction of the inclosed air, then heat- 

 ing them again, the generated steam carrying 

 off the air of the flask, and again immersing the 

 open end and cooling ; this was repeated a 

 number of times, a quantity of the infusion be- 

 ing driven up into the flask each time upon the 

 condensation of the steam, until they were 

 about four fifths full of the liquor. They were 

 next plunged in a bath of heated oil and kept 

 at the boiling point, which is a fraction above 

 212 F., the oil being heated to 250. After 

 boiling five minutes the flasks were lifted part- 

 ly out with a pair of tongs, and while a lamp 

 was held under the middle of the neck it was 

 drawn out by another pair of tongs until it 

 closed and broke off. 



In the summer of 1877 Tyndall carried sixty 

 such flasks, thus -partly filled with strong infu- 

 sions of beef, mutton, turnip, and cucumber, and 

 thus hermetically sealed, to the Alps. On open- 

 ing the box at the Bel Alp, six of the flasks 

 were seen to be full of infusoria, as the liquid 

 had turned muddy in color, and on examination 

 it was found that the tender tips of the necks 

 had been broken off in the transport from Lon- 

 don. Four more of the glass bulbs were acci- 

 dentally broken. The remaining fifty flasks 

 were exposed to the warm rays of the summer 

 sun in the daytime, and hung in a warm 

 kitchen at night. At the end of a month they, 

 were found as clear as in the beginning. They 

 were then subjected to the crucial experiment. 

 The opponents of the germ theory might justly 

 urge that the fact that organic matter can be 



