tioned. This time-serving and popular verdict once announced, was received with all the more readiness, because others, not having exercised the necessary care, had for a time failed to confirm my results. Now, however, that the facts have been substantiated and are generally acknowledged, the subsequent course of events has made it useful to ask, Why the majority of persons competent to judge, previously received the statements referred to with so much incredulity? To this question only one answer can be given. The results were discredited because it was a generally accepted belief amongst men of science that exposure to the temperature of boiling water would have killed all pre-existing Living Matter within the flasks. And this being the case, the appearance of swarms of Bacteria in the experimental fluids in the course of a few days could only be explained by the supposition that what has been called 'Spontaneous Generation' had occurred. To acknowledge this, however, was rank heresy, and was in opposition to some of the most cherished and sacred beliefs of many men of scie In such an emergency what were scientific in vestigators to do? Should they equivocate and, without definite trial as to the truth or untruth of their old belief in the destructive influence of boiling water, at once cast it aside? This would certainly seem a strange course to pursue, seeing that a strong belief in the lethal effects of boiling water had been the measure of their previous profound unbelief of facts now demonstrated to them! Yet this course was in some respects the easiest-it would expose those who followed it to less external friction, and it allowed them still to hold fast to a long-cherished conviction as to the truth of the dogma omne vivum ex vivo, which they perhaps found it impossible to throw aside. But whatever extenuating circumstances might be pleaded, it cannot be concealed that the course actually adopted was not the method by which men of science usually pursue their investigations. The question of 'Spontaneous Generation,' therefore, at present stands in this position. If it be really true that all known forms of Living Matter are killed by a brief exposure in the moist state to the temperature of 212° F., there is no longer room for doubt. The occurrence of 'Spontaneous Generation' must in this case be admitted as an established fact, or Law of Nature.' But the evidence now in our possession concerning the death-point of heated Living Matter all tends to show that it is killed at a temperature below that of boiling water, as will be seen by the facts recorded in the last essay of this volume. The two previous papers, moreover, contain the records of experiments proving that Bacteria and their germs are killed at 140° F.-these being the very organisms that most frequently make their appearance in the fluids within closed experimental vessels which have been previously heated to 212° F. In the present aspect of the question, therefore, these three papers contain all the evidence needed for the establishment of the occurrence of 'Spontaneous Generation.' In the two parts of the first essay, however, I have endeavoured to show that the acknowledgment of this natural origin of Living Matter carries with it no contradictions, and is indeed in accordance with the present state of scientific knowledge. I have further striven to give, in brief compass, a synopsis of other evidence in favour of Archebiosis and Heterogenesis (the two processes now included under the phrase 'Spontaneous Generation'); to indicate some of the modifications in biological doctrine which a belief in the present occurrence of these processes will necessitate; and generally to show, to the best of my ability, the weakness and untenability of the old view. In the execution of a task so complicated and difficult, there must necessarily be many imperfections. I am anxious, however, to promote what I consider to be the cause of truth, and have therefore collected the papers included in the present volume, in the hope that they may be of some little use and interest to those desirous of obtaining information on the present aspect of the great questions to which they relate. QUEEN ANNE STREET, CAVENDISH SQUARE, |