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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



consideration when we come to the discussion of 

 the bacterial death-point. There exists no very 

 definite account of any confirmation of these ex- 

 periments, but to a certain extent they were veri- 

 fied by Bastian and others as regards the tem- 

 perature of 100° ft, and they derive great weight 

 from the acknowledged experimental skill of M. 

 Pasteur. 



The only other experiments to which we need 

 refer, on the point now under consideration, are 

 the very elaborate series conducted by Prof. Tyn- 

 dall since the Bastian-Sanderson report. These, 

 like Pasteur's, have not been precisely repeated, 

 but Prof. Tyndall's position is such as to render 

 a careful discussion, even of his isolated work, 

 extremely interesting. It is, perhaps, to be in- 

 ferred, from the emphasis with which Prof. Tyn- 

 dall restricts his statements to purely liquid in- 

 fusions, that he has gone over and confirmed 

 Bastian's turnip and cheese experiments, but he 

 did at one time (whatever he does now) maintain 

 that no purely liquid infusion, whether acid or 

 alkaline, could putrefy if boiled and protected 

 from the contact of atmospheric dust. His ex- 

 periments were conducted in two series, one de- 

 scribed in a lecture at the Royal Institution early 

 in 1876, published in a more mature form in the 

 " Transactions of the Royal Society " for that 

 year, and the other in a lecture delivered at the 

 Royal Institution on the 19th of January in the 

 present year, a report of which appeared in the 

 British Medical Journal of January 27th. The 

 general method employed was to cement a large 

 number of test-tubes through the bottom of a 

 box with their lower ends protruding, so as to 

 admit of the application of heat. The box was 

 closed and made air-tight, and a pipette provided 

 for filling the tubes with such organic fluids as 

 might be desired. The air within the box was, 

 as the professor considered, absolutely purified 

 from germs by subsidence, the interior of the 

 box being coated with glycerine, to imprison 

 whatever dust might fall upon it, and the com- 

 pletion of this process was determined by the 

 use of the electric beam. A connection with the 

 outer air was established through bent tubes and 

 plugs of cotton-wool, which were thought to af- 

 ford adequate protection against the intrusion of 

 germinal matter. Why this roundabout and un- 

 certain method of procedure was preferred to 

 much simpler well-known means it is difficult to 

 say ; but in the first series of experiments it led 

 to no catastrophe. Various infusions were in- 

 serted in the test-tubes by means of the pipette, 

 which was carefully guarded against the passage 



of air otherwise than through wool. The tubes 

 were heated for a few minutes by immersion in 

 an oil-bath, and left in the laboratory to evolve 

 life if they could. The temperature of incubation 

 was not taken, but Prof. Tyndall stated afterward 

 that a temperature of 90° Fahr. was "generally 

 attainable " in the laboratory, and that on mild 

 days and in favorable positions the temperature 

 to which the infusions were subjected reached 

 over 100°. All of them remained barren, in- 

 cluding any neutral solutions among them, which, 

 according to Pasteur, ought to have putrefied. 

 In the present year the same experiment was re- 

 peated, at the Royal Institution, with the oppo- 

 site result. Most of the infusions became putrid, 

 in some instances more rapidly than what were 

 intended to be precisely similar infusions exposed 

 to the outside air. The experiment was repeated 

 with an improved arrangement of the pipette, 

 which had fallen under suspicion from the con- 

 duct of the infusions, but still with the same re- 

 sult. Then the incoming air was cleansed not 

 only by the wool-filter, but by calcining it by 

 means of red-hot platinum, but still with no 

 change in the result. Another box was then ex- j 

 perimented on at Kew, and this time the infu- 

 sions remained pure with one exception, after 

 having been kept for a time — not, we think, spe- 

 cified — in a temperature varying from 80° to a 

 little over 90°, a degree of incubating heat not 

 the most favorable, but which has very often 

 been found sufficient to develop life. The con- 

 flicting results of these experiments were ingen- 

 iously accounted for by Prof. Tyndall — the fail- 

 ure at Kew being ascribed to a pin-hole, and 

 those at the Royal Institution to the insufficiency 

 of bent tubes, cotton-plugs, and red-hot platinum, 

 to keep out or kill living germs at Albemarle 

 Street, though they are still relied on as sufficient 

 in a purer atmosphere, and were found so last 

 year in the Royal Institution itself. The special 

 theory resorted to to explain the contrast be- 

 tween the experiments at the Royal Institution 

 in the two successive years is that in 1877 that 

 atmosphere was charged with bacterial germs in 

 such excess as to be proof against subsidence, 

 burning, and plugging, and that this excess was 

 due to the fact that in one of the rooms of the 

 institution some old hay was to be found. How 

 far this deserves consideration as a working hy. 

 pothesis is a question which admits of difference 

 of opinion ; but Prof. Tyndall would scarcely ask 

 us to accept it without proof as the real expla- 

 nation. Why bacterial germs in excess should 

 make their way through a sieve ordinarily close 



