It has been stated that in cases of suffocation the heart continues to contract for a short period, after the cessation of breathing; that this interval is extremely short, but liable to vary from several causes; and that it is uniformly shorter in cases of death by drowning, than in those by strangulation. To the physician this is an interval of anxiety and importance; let him beware how he trifles with the fleeting moments, in which alone the resources of his art can be of any avail. If artificial respiration be established at this period, the blood will become once more oxygenised, the action of the heart will be continued, the scarlet blood will be transmitted to the brain, and sensibility will therefore return; the nervous energy will be once more transmitted to the respiratory organs, and the animal will at length make a voluntary effort to inspire air. Here then is the interval of time, during which artificial breathing may be employed so as to effect a restoration to life, where death must otherwise have been inevitable. Mr. _Brodie_ has made a great variety of interesting experiments upon this subject, from which may be deduced the following important corollaries. 1. If the lungs be inflated, the action of the heart will continue. 2. If the action of the heart has become feeble, but the circulation is nevertheless not entirely suspended, the inflation of the lungs will cause the feeble actions to become again frequent and vigorous. 3. If the action of the heart has entirely ceased, it is impossible to restore it by the inflation of the lungs. 4. If the action of the heart has not entirely ceased, but is so feeble as no longer to maintain the circulation, the artificial respiration will prove as useless, as if the heart were perfectly motionless. There is still, however, another period at which artificial respiration may be employed with the greatest advantage; we have stated that after the natural respiration has been re-established, and the animal would appear to be advancing towards recovery, it not unfrequently relapses into a state of insensibility, becomes convulsed, and dies. As this depends upon the black blood which is circulating through the brain, so paralysing that organ as to prevent a necessary transmission of its influence to the muscles of respiration, life may be preserved if artificial respiration be established until the brain is again supplied with duly oxygenized blood; after which the animal will be enabled to perform its own functions without any assistance from art. The same treatment will, of course, apply in every case where the natural respiration ceases in consequence of being deprived of a due supply of nervous energy, from the insensibility of the brain; as from a blow on the head—the action of a narcotic poison—from lightning?