tions in a great number of instances, after the introduction of a limited quantity of air, the genetic power of the infusions had not been destroyed by the material conditions of the experiments. Besides, this objection, which has been raised ever since the earliest controversies between the heterogenists and the panspermists, has been definitely answered by an experiment made by M. Pasteur; he received in a flask, exhausted and deprived of living germs by the momentary application of a sufficiently high temperature, some blood at the instant that it left the organism, and without allowing this liquid, which is so peculiarly putrescible, to come in contact with air. By permitting air deprived of germs, either by calcination or simple filtration, to enter the flask, and then hermetically sealing it, he found that the blood was preserved for an indefinite period intact, although it had not been exposed to heat.
M. Pasteur has also shown that air may be deprived of germs by its passage through a capillary tube bent upon itself. It is, therefore, sufficient, in most cases, to draw out the neck of the flask so as to form a very long, narrow tube, which is bent in several directions, as, for example, in Fig. 5. When the air originally contained in it has been expelled, and the preëxisting germs killed by prolonged boiling, the flask is allowed to cool slowly.
In closing our account of M. Pasteur's interesting memoir, in which heterogenesis was driven to its last intrenchments, we must add that this learned chemist endeavored to deprive his adversaries of one of their principal arguments. Experiments on spontaneous generation have always been conducted with vegetable or animal infusions; it was supposed by Needham, Buffon, and Pouchet, that organisms were only thus produced at the moment of expiring Nature, when the elements of the beings on which they are developed are entering into new chemical combinations, and are passing fully through the phenomena of fermentation or putrefaction.
In other words, albuminoid matters preserve in some degree a certain reserve of vitality, which would allow them to become organic by contact with oxygen, when the conditions of temperature and humidity are favorable. Starting with the idea that albuminoid substances are only aliments for the germs of infusoria, mucidines, or ferments, M. Pasteur has proved directly that organic substances may be replaced by those which are purely mineral or artificial, or, at least, by substances on which this imaginary vegetative force cannot be supposed to have any influence.
