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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



would be taken toward the settlement of the 

 greatest problem which now divides the scientific 

 world. 



The evidence on the point which has hitherto 

 been examined may be thus summed up : 



1. It is established beyond dispute that a turnip- 

 infusion, with cheese-dust added, will produce life 

 after having been boiled and protected from con- 

 tact with the atmosphere or anything it may con- 

 tain. 



2. The like fact has been ascertained by Iluit- 

 zinga when soluble peptone was substituted for 

 cheese-dust, and no counter-experiments on this 

 point have ever been made public. 



3. The like fact with reference to other purely 

 liquid infusions has been alleged by Bastian, ac- 

 knowledged after jealous scrutiny by Sanderson, 

 confirmed by Huitzinga and Cohn, and (when the 

 solution is not acid) by Pasteur, the chief of the 

 germ-theory school. But Bastian's conclusions 

 and Pasteur's conclusions are equally denied by 

 Prof. Tyndall, mainly on the strength of his own 

 unconfirmed experiments. 



A theory was once started to the effect that 

 the fertility of the turnip and cheese mixture 

 might be due to the hypothetical fact that minute 

 fragments of cheese-dust would protect any 

 germs within them from attaining the temperature 

 of boiling water during a period of five or ten 

 minutes. To any one who ever boiled an egg 

 this notion will seem too childish to need an 

 answer; and, if there were anything in it, it 

 would avail nothing for the germ-theorists until 

 they had displaced Huitzinga's conclusion that 

 soluble peptone will serve the purpose as well as 

 cheese. 



On the balance of evidence as it now stands 

 there seems little to justify a doubt that organic 

 substances, after being raised to 212° Fahr., will 

 often produce life, though protected from all ac- 

 cess of germs from without. But this proposition 

 is very far from establishing the theory of spon- 

 taneous generation. To do so it is needful also to 

 prove the further proposition that a moist tem- 

 perature of 212° Fahr. is sufficient to destroy life, 

 not only in bacteria but in any germs which they 

 may throw off; and this is beyond question the 

 most difficult part of the inquiry. 



At the outset there is this puzzle : We know 

 that bacteria ordinarily multiply by fission. We 

 do not know whether they may not also multiply 

 by germs. If they do, these germs are ultra- 

 microscopic objects, though possibly discernible, 

 en masse, by the aid of Tyndall's electric beam. 

 It would seem to follow, therefore, that except 

 from analogy we can know nothing about the 



qualities of such hypothetical germs, and are 

 utterly unable to predicate what their powers of 

 resisting heat may be. But science is not quite 

 so helpless as this. When bacteria are clouding 

 a fluid with their rapid increase, it may not un- 

 warrantably be supposed that there are present 

 the parents and their germs in every stage. If, 

 therefore, we can find the temperature which will 

 destroy the reproductive power of such a fluid, 

 we may reasonably infer that we have discovered 

 the heat which will kill or (what is absolutely the 

 same thing for the purposes of our investigation) 

 render inert any germs which they may be capa- 

 ble of engendering. But when this difficulty is 

 surmounted there is yet another : What test can 

 we apply to determine whether such death has 

 been produced ? If we place them in a suitable 

 nutritive fluid, and the bacterial colony is found 

 to increase and multiply, how are we to know 

 whether the population is the offspring of germs 

 undestroyed by the heat applied or the de novo 

 product of the matrix fluid itself? Once assume 

 as a starting-point the germ -theory, and the 

 ascertainment of the death-point of bacterium 

 germs is the simplest thing in the world. If life 

 appears in the fluid inoculated with them, say at 

 once that it is due to the germs, and that the heat 

 was not enough to kill them. If, on the other 

 hand, the fluid remains barren after the germs 

 have been introduced, it follows that the heat was 

 fatal. For the purpose of testing the validity of 

 the germ-theory, it is obvious that no such petitio 

 principii can be for a moment admitted ; and yet, 

 oddly enough, it was only by this deliciously 

 naive reasoning that Pasteur supported his view 

 of the vital resistance of bacterial germs. He 

 found that one or two acid fluids with which he 

 worked would not putrefy after being heated to 

 the boiling-point, and he inferred (so far legiti- 

 mately enough) that no germ could (in such a 

 fluid) sustain the temperature of 100° C. He 

 also found that one or two neutral or faintly al- 

 kaline fluids would putrefy after boiling, though 

 they failed to do so if heated to 110°, or even 

 105°. He thereupon straightway assumed that 

 putrefaction could not come without germs, and 

 therefore declared that germs heated in these 

 non-acid fluids could survive a temperature of 

 100°, though they succumbed to a slightly greater 

 heat. Of course this inference was idle while 

 the germ-theory itself was in question, and some 

 independent method of fixing the death-point 

 remained to be discovered, if ever it was to be 

 fixed at all. 



If it were, only possible to find a test-fluid 



