In the first place, it must be noticed that in the phenomena of hibernation we have what at a first view seems closely to resemble the results of Signor Rotura's apocryphal experiments. As was remarked in the _Times_, the idea underlying the Australian story is that the hibernation of animals can be artificially imitated and extended, so that as certain animals lie in a state of torpor and insensibility throughout the winter months, all animals also may perhaps be caused to lie in such a state for an indefinite length of time, if only a suitable degree of cold is maintained, and some special contrivance adopted to prevent insensibility from passing into death. The phenomena of hibernation are indeed so surprising, when rightly understood, that inexperienced persons might well believe in almost any wonders resulting from the artificial production (which, be it remembered, is altogether possible) of the hibernating condition, and the artificial extension of this condition to other animals than those which at present hibernate, and to long periods of time. It has been justly said, that if hibernation had only been noticed among cold-blooded animals, its possibility in the case of mammals would have seemed inconceivable. The first news that the bat and hedgehog pass into the state of complete hibernation, would probably have bean received as either a daring hoax or a very gross blunder. Let us consider what hibernation really is. When, as winter approaches and their insect food disappears, the bat and the hedgehog resign themselves to torpor, the processes which we are in the habit of associating with vitality gradually diminish in activity. The breathing becomes slower and slower, the heart beats more and more slowly, more and more feebly. At last the breathing ceases altogether. The circulation does not wholly cease, however. So far as is known, the life of warm-blooded animals cannot continue after the circulation has entirely ceased for more than a certain not very considerable length of time.[73] The chemical changes on which animal heat depends, and without which there can be no active vitality, cease with the cessation of respiration. But dormant vitality is still maintained in hibernation, because the heart's fibre, excited to contract by the carbonized blood, continues to propel the blood through the torpid body. This slow circulation of venous blood continues during the whole period of hibernation. It is the only vital process which can be recognised; and it is not easy to understand how the life of any warm-blooded animal can be maintained in this way. The explanation usually offered is that the material conveyed by the absorbents suffices to counterbalance the process of waste occasioned by the slow circulation. But this does not in reality touch the chief difficulty presented by the phenomena of hibernation. So far as mere waste is concerned (as I have elsewhere pointed out) the imagined Australian process is as effectual as