BIOLOGICAL LECTURE.

Otago Witness, Issue 1602, 5 August 1882, Page 23

BIOLOGICAL LECTURE.

The third and last of a very interesting series of lectures on " Fermentation and Putrefaction" was delivered by Prof essor Parkerin the Museum on Saturday evening. The excessively stormy weather unfortunately prevented the usual good attendance, but some 30 persons braved the elements in order to hear the conclusion of a subject which has been followed with great interest by the audiences on each former occasion. Spontaneous generation, heterogenesis, and the germ theory of disease were the branches of the subject dealt with by Professor Parker on Saturday. _ The theory of spontaneous generation, or abiogenesis, it was explained, supposed that living organisms arose de novo, either from inorganic matter or from dead organic matter. It was opposed by the theory of biogenesis, or panspermism, which supposed that life only came from pre-existing life, at least so far as observation and induction could be carried. The belief in spontaneous generation was formerly universal, and Aristotle in his history of animals stated clearly that some organisms sprang from putrid matter, certain insects from the dew, &c, &c. Plutarch even said that the soil of Egypt was capable of producing rats, and at the present day there were many of the uneducated classes who believed in the spontaneous generation of frogs. The first blow to the theory was given in 1638 by the Italian Redi, who proved that if meat, which was particularly liable to corruption from maggots, were covered securely by a wire screen, these maggots did not appear. Redi thus demonstrated that these really arose from eggs laid upon the meat by^ flies. No one now pretended that the higher organisms arose spontaneously, In modern times, inquiry as to the theory of "abiogenesis had all centred around bacteria and monads, the lowest existing organisms. The whole issue was narrowed down to this : If any fluid capable of putrefaction was exposed to the air, putrefaction would inevitably occur, and this was always accompanied by the appearance of bacteria and monads. The question was, were these of spontaneous generation, or were they the result of germs in the air finding their way to the fluid ? To prove this latter theory, it was necessary to show that if the access of germs to a putrescible fluid (the existing germs in which had been previously destroyed by heating) were prevented, the fluid would show no signs of life, The presence of germs of some sort in the air had been proved by filtering air and examining suspended particles, and their access to putrescible fluids, previously sterilised by boiling, had been prevented in various ways. These were :— (1) By hermetically sealing the containing vessel during ebullition. (2) By allowing the access of calcined air only. (3) By filtering air through cotton wool. (4) By filtering it through long fine tubes, as performed by Pasteur. (5) By allowing the germs to subside in a confined space of still air, as performed by Professor Tyndall. The invariable result of experiments properly conducted in this way had been to show that putrescible fluids thus confined did not putrefy, (the lecturer illustrated this by showing his

audience various experiments, performed' months ago, on such fluids as milk, infusions i of fish, meat, turnips, &c, putrefaction having in each case been completely prevented, lias, to him, appeared convincing proof of the fallacy of the doctrine of spontaneous generation or. abiogenesis. As regarded the theory of heterogenesis, it supposed that well-characterised organisms arose by transformation in the, course of a single generation of other organ-, isms ; and it was opposed by the theory of homogenesis, according to which offspring always resembled the parent in essential characteristics. Researches into the develop- 1 merit of animals and plants showed a definite' series of changes to be always gone through m the passage from the embryonic to the adult state, and this showed hpterogenesis to be inherently improbable, all cases in which itj had been supposed to occur having been due to erroneous observation. The lecturer concluded by dealing with the germ theory of disease, which had been proved to be true in pertain cases by establishing a definite connection between phases in the life history of bacteria and phases of the disease. [