Licence: Public Domain Mark
Credit: The germ theory again. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![[ 71S CHAMBERS’S JOURNAL. they say, the germs must have entered into them by some means or other ; and if he superheated these fluids, the fact of the germs surviving the process shews that they must be possessed of greater enduring power than we have given them credit for. Curiously enough, Professor Tyndall declares that frequent applications of a low degree of heat, and applied at intervals, have a far greater ‘sterilising effect’ than a single application of a high temperature. For a given fluid may contain germs of all ages. If such a fluid be boiled for a considerable time, all the germs of recent forma- tion will he killed ; but those of a greater age will merely be softened, but still capable of reanima- tion. If, however, the fluid be heated for a short time only, the recent germs will be destroyed, while an older crop will be liberated. A second application of heat destroys this second crop, and brings a third into play. Further heat will awaken successive crops, until at length a point is reached when the toughest germ must yield. This is certainly a most ingenious explanation of the difficulty. A very interesting contribution to this subject has lately been made by Dr Bastian and others; and we will now briefly describe the main results of their researches. It has long been known that slightly alkaline organic fluids are more difficult to sterilise than those which are slightly acid. Pasteur the French chemist says that animal water in its normally acid state becomes sterile at one hundred degrees centigrade; but that if the infusion is first rendered alkaline by the addition of potash, the application of a little more heat is necessary, in order to insure sterility. If we bear in mind the two theories, we shall see that these observations of Pasteur may be explained according to either of them. We may believe that the germs in the infusion are fortified against the destructive action of heat by liquor potassae ; or on the other hand, we may hold that the spontaneous generation of organisms is favoured by the presence of an alkali. Acting upon these data, Dr Bastian heated a similar fluid in its acid condition to the tempera- ture of one hundred degrees; so that, according to Pasteur, it was now barren. He then added a quantity of potash sufficient to neutralise the acid, the addition of the alkali thus being made after instead of before the boiling ; and he then allowed the fluid so treated to stand at a temperature of about one hundred and fifteen degrees Fahrenheit. In a short time swarms of bacteria appeared. Dr Roberts, however, considers that this result was obtained because sufficient precaution had not been taken by Dr Bastian to prevent the entry of germs, which might have been introduced by the potash. Accordingly, he filled a' small flask with an ounce of the acid infusion, and then sealed up his potash in a capillary tube. The potash was then heated in oil to two hundred and eighty degrees Fahrenheit, and kept for fifteen minutes. The tube of potash was now introduced into the flask containing the infusion, and the flask was boiled for five minutes, and sealed. The flask was now kept for some time in order to test its sterility. When this was ascertained, the flask was shaken, so that the little tube of potash inside was broken, and the potash was thus allowed to mingle with and neutralise the infusion. The flask was now maintained at a low temperature of one ^ hundred and fifteen degrees Fahrenheit, and it remained perfectly clear. And so Dr Roberts con- cludes that liquor potassae has no power to excite the generation of organisms in a sterilised infusion. Professor Tyndall repeated these experiments with additional precautions, and obtained similar results. The general conclusion which is drawn from various experiments by the advocates of the Germ theory is, that liquor potassae has no in- herent power to stimulate the production of bacteria, and that any apparent power of this kind which it may seem to possess is due to the presence of germs within it. These germs they consider are not destroyed until the potash has been raised to the temperature of one hundred de- grees centigrade if solid, and to one hundred and ten degrees centigrade if liquid. Dr Bastian, who repeated his former experiments with every possible precaution, found no difference in his results. Moreover, he discovered that liquor potassae, when added in proper quantities, is just as efficacious in stimulating the development of life after it has been heated to one hundred and ten degrees centigrade, as when it has been heated to only one hundred degrees. Pasteur will con- sequently have to raise the temperature which he considers sufficient to destroy the germs contained in a solution of strong liquor potassae to a point still higher than one hundred and ten degrees. But there is still another proof that liquor potassae if previously heated to one hundred de- grees does not induce fermentation in virtue of its germs, because if only one or two drops be added, the infusion will remain as barren as ever; while a few more drops will immediately start the process of fermentation. Now if the potash really induced fermentation because it brought germs along with it, two drops would be quite as efficacious as any other amount. Finally, Dr Bastian has shewn us that an excess of alkali prevents fermentation, and to this fact he attributes the failure of Pasteur tc develop life when he employed solid potash. He had added too much of the alkali It is impossible to draw any definite conclusion from these as from the other experiments, until we know the precise temperature which is fatal tc germinal life. Dr Bastian indeed thinks that he has been able to shew that bacteria and theii germs cannot exist at higher temperatures than one hundred and forty degrees Fahrenheit; but his evidence here is not quite conclusive. He does not deny the existence of germs nor] their probable influence in producing life; he merely says that his experiments furnish evidence to shew, that in some cases organisms may spring into existence without the aid of a parent. The strong points of his case are, that as fast as his adversaries can suggest precautions to insure the destruction of germs, he has been able to shew life under the altered conditions ; and that whenever the sup-, posed death-point of bacteria has been raised on account of his experiments, he has succeeded in j obtaining life after having submitted his flasks tc 1 . the required temperatures. _ j| How this most interesting controversy will end. we cannot foretell; but we hope that the further i researches of our scientific men upon the subject! will ultimately lead to the discovery of the truth. Meanwhile, we observe that Dr Richard-j son, at the late Sanitary Congress at Leamington. ,f entirely dissented from the theory of germs being B](https://iiif.wellcomecollection.org/image/b22468511_0004.jp2/full/800%2C/0/default.jpg)
