This phenomenon is one of the most remark able presented to me in the whole animal king dom. It forms the single exception to the most general rule amongst animals which pos sess a double heart. It accounts for the possi bility of immersion in water or a noxious gas, without drowning or asphyxia; and it accounts for the possibility of a suspended respiration, without the feeling of oppression or fain, although sensation be unimpaired. It is, in a word, this peculiar phenomenon, which, con joined with the peculiar effect of .sleep in in ducing diminished respiration in hibernating animals, constitutes the susceptibility and capa bility of taking on the hibernating state. On the other hand, as the rapid circulation of a highly arterialized blood in the brain and spinal marrow of birds probably conduces to their activity, the slow circulation of a venous blood doubtless contributes to the lethargy of the hibernating animal.
I need scarcely advert to the function of delffeation. It has already been briefly noticed under the head of sanguification, with which it proceeds part passu.
In regard to the nervous system, I can only repeat that sensation and volition are quiescent.
In my memoir upon the subject of hibernation,* I committed an error relative to this subject. But I am now satisfied that what I considered to be evidences of an unimpaired sensibility, were phenomena of the excito-motorykind. Thus I have observed that the slighest touch applied to one of the spines of the hedgehog immedi ately rouses it to draw that deep inspiration of which I have spoken. The merest shake in duces a few respirations in the bat. The least disturbance, in fact, is felt, as is obvious from its effect in inducing motion in the animal.
It is from the misconception on this point that the error has arisen, that the respiration is not absolutely suspended in hibernation. This function has been so readily re-excited, that it has been considered as appertaining to the state of hibernation.
As I have already stated, the cerebral func tions sleep, the true spinal functions retain their wonted energy; and if the respiration be nearly suspended, it is because little carbonic acid, the excitor of respiration, is evolved.
In the midst of a suspended or partially sus pended respiration, the irritability of the mus cular fibre becomes proportionately augmented.
The single fact of a power of sustaining the privation of air, without loss of life, leads alone to the inference that the irritability is greatly augmented in the state of hibernation. This
inference flows from the law already stated, and the fact is one of its most remarkable illus trations and confirmations.
It might have been inferred from these pre mises, that the beat of the heart would continue longer after decapitation in the state of hiber nation than in the state of activity in the same animal; an inference at once most singular and correct.
This view receives the fullest confirmation fmm the following remarkable experiment : on March the 9th, soon after midnight, I took a hedgehog which had been in a state of uninter rupted lethargy during 150 hours, and divided the spinal marrow just below the occiput; I then removed the brain and destroyed the whole spinal marrow as gently as possible. The action of the heart continued vigorous during four hours, when, seeing no prospect of a termination to the experiment, I resolved to envelope the animal in a wet cloth, and leave it until early in the morning. At 7 o'clock A.M. the beat of both sides of the heart still continued. They still continued to move at 10 A.M., each auricle and each ventricle con tracting quite distinctly. At half-after 11 A.M. all were equally motionless ; yet all equally contracted on being stimulated by the point of a penknife. At noon the two ventricles were alike unmoved on being irritated as before; but both auricles contracted. Both auricles and ventricles were shortly afterwards unirritable.
This experiment is the most extraordinary of those which have been performed upon the mammalia. It proves several interesting and important points : 1. That the irritability of the heart is augmented in continued lethargy in an extrannlinary degree. 2. That the irritability of the left side of the heart is then little, if at all, less irritable than the right,—that it is, in fact, veno-contractile. 3. That, in this condi tion of the animal system, the action of the heart continues for a considerable period inde pendently of the brain and spinal marrow.
On April the 20th, at six o'clock in the even ing, the temperature of the atmosphere being 53°, a comparative experiment was made upon a hedgehog in its state of activity: the spinal marrow was simply divided at the occiput; the beat of the right ventricle continued upwards of two hours, that of the left ventricle ceased almost immediately ; the left auricle ceased to beat in less than aquancr of an hour; the right auricle also ceased to beat long before the right ventricle.