[[p. 178]] It may be as well to state at the outset that the present volume is not Dr. Bastian's long-promised work on "The Beginnings of Life;" and it would have been better had some title been devised to prevent the confusion that will inevitably be caused by its appearance at this juncture. We have here, however, a condensed sketch of the whole controversy on Spontaneous Generation, and a statement of some very important researches conducted by the author since the discussion which followed Prof. Huxley's Presidential Address at Liverpool last September. It will be remembered that the objections to Dr. Bastian's experiments and to the results he deduced from them were twofold. It was said that we have no proof that these minute organisms (Bacteria, &c.), or their germs cannot resist the heat to which they were subjected. It was also said that no proof was given that the supposed organisms found by Dr. Bastian in these boiled and hermetically sealed liquids were alive. The motions exhibited might be "Brownian" motions, and the experimenter probably found nothing in his vessels but what he put into them. The answer to these objections is now given. The test of vitality is said to be, not movement, which is admitted to be uncertain, but the power of reproduction. It is found that if a portion of liquid containing Bacteria is divided into two parts, one of which is boiled, and a drop from each of these portions is mounted as a microscopic object, under a covering glass surrounded by quickly-drying cement, the unboiled specimen exhibits a marked increase from day to day in the quantity of imprisoned Bacteria, while the boiled specimen continues unchanged during the same time. Making use of this test of vitality, it was next ascertained what degree of heat was fatal to these low organisms. By using a lower and lower temperature, it was found that exposure to 140° F. for ten minutes destroyed Bacteria, while after exposure to 131° F. for the same time they rapidly multiplied. Somewhat higher organisms-- Vibrios, Amœba, Monads, Vorticellæ, &c., were, however, killed by exposure to 131° F. for five minutes. It was subsequently ascertained that a four hours' exposure to a temperature of even 127° F. destroyed Bacteria and Torulæ. It is argued that, as in all these experiments the solutions used swarmed with Bacteria, &c., in various stages of increase their hypothetical "germs" cannot be supposed to have been entirely absent; and that we may therefore conclude that the "germ" has no greater power of resisting heat than the animal itself.

    Dr. Bastian also criticises many of the experiments of Pasteur, and the arguments founded on them. He maintains that the corpuscles found by the latter to exist in the atmosphere, and which "resemble" spores of fungi, have never been proved to be such; and even if they were so proved, it would not account for the constant occurrence of Bacteria and other low organisms, whose "germs" are quite unknown, and which there seems no reason to believe could retain their vitality in a dry state [[p. 179]] in the atmosphere. The fact that vessels with bent necks or with plugs of cotton-wool do not produce organisms, while other vessels not so protected produce them in abundance, is shown, by numerous experiments, not to be universal. The evidence now adduced is held to prove that a variety of conditions hitherto not attended to affect the result, such as temperature, the strength of the solution, and especially the presence of particles of organic matter, other than "germs," derived from the atmosphere. A summary is given of sixty-five comparative experiments, which are believed to show, among other things, that the non-production of Bacteria, &c., in infusions and other suitable liquids, is so common an occurrence that the negative experiments of Pasteur and others have no weight as compared with the positive results obtained by a considerable number of observers, to whom the author refers, as well as by himself.

    Some of these comparative experiments are very suggestive. Hay infusion, for instance, exposed to air, produced abundance of Bacteria in forty-eight hours, and these had increased considerably in sixty-eight hours. A similar infusion, sealed up after the fluid had become cold, behaved in a similar manner. The same in a flask with neck two feet long and having eight acute flexures, remained unchanged for twelve days. A similar infusion, hermetically sealed during ebullition, on the other hand, showed turbidity in forty-eight hours, which subsequently increased, and Bacteria, Vibriones, Leptothrix, and Torulæ were found in abundance. Here, then, whatever inference may be drawn from the first three experiments is entirely negatived by the fourth. Other experiments show that ammonia-tartrate solution sealed in vacuo at a temperature of 90° F. produced in eighty-four hours abundance of Bacteria; while the same solution, if boiled at 212° F. and exposed to the air in flasks covered with paper caps, remained quite clear for nine days; yet as soon as it was inoculated with living Bacteria, they increased rapidly and produced turbidity. These, and a number of other equally suggestive experiments, indicate that the conditions favourable to the origin and to the increase of these low forms are not always identical. Both are very complex, and we cannot avoid the conclusion that the advocates of the universal germ theory have been somewhat hasty in founding their doctrine upon insufficient data, for the most part of a negative character.

    We have here, undoubtedly, an important addition to the experimental evidence by which alone the question can be decided, and we are glad to observe the unprejudiced and philosophical spirit with which Dr. Bastian discusses this most interesting and important problem.