4. Later experiments and observations have, however, shewn that this explanation likewise is, in some measure, incorrect. In fact, while the free flow of venous blood in the carotid arteries of an asphyxiated animal was urged with perfect fairness by Bichat, as a refutation of the theory of Goodwyn, it was with equal justice argued by Goodwyn,* in opposition to Bichat, that if the heart's actions ceased in asphyxia, only because its substance is pene trated by venous blood from the coronary arte ries, these actions could not be restored by blowing air into the lungs and arterializing the blood there.
Bichat, indeed, foreseeing • this objection, maintained that the artificial respiration never is successful in restoring the circulation, unless employed in the interval which, as was already stated, always exists between the occurrence of insensibility and the final cessation of the circu lation. But subsequent and careful observa tions (e.g. those of Roesler, Edinburgh Journal, vol. xxiii) show that life has been restored, by this means, after warm-blooded animals have lain from twelve to seventeen minutes after their immersion in water, i. e. until a time when all observations made by laying open the chests of similar animals show that their circulation must have ceased. The records both of the Humane Society in London and of a similar institution in Paris, seem sufficiently to show that resuscitation has occasionally taken place in the human body after fifteen minutes' im mersion.- And we are therefore well assured that the arterialization of the blood at the lungs may, in some instances, restore the natural state of the heart's action after the circulation has come to a stand.
Farther, although there is a laboured attempt, by Bichat,t to explain the accumulation of blood on the right side of the heart, and the comparative emptiness of the left side, in as phyxia, consistently with his own explanation of the failure of the circulation ; yet it seems obvious, that if that explanation were correct, the left side of the heart, receiving the venous blood and contracting on it until it loses its power from the penetration of its own fibres, should be found after death distended with that blood ; and that the accumulation of blood taking place in the lungs and right side of the heart, indicates that the capillaries of the lungs are the main seat of the cause which ultimately stops the circulation.
That this is really the faCt has been more unequivocally shown, first, by the experiments by Dr. Williams, and afterwards by those of Dr. Kay,* which we know to have been care fully performed, and sufficiently repeated, and which appear to solve satisfactorily all the diffi culties that have been stated. Bichat had not adverted to the length of time during which the circulation of venous blood by the left side of the heart, is carried on in asphyxia; but the experi ments of both Dr. Williams and Dr. Kay prove,
that this time is very short, and that before this side of the heart has lost its contractile power, the pulmonary veins have ceased to deliver the blood to it, in such quantity as to maintain any effec tive action. A short quotation from Dr. Kay's paper will show the evidence for this propo sition.
44 Experiment 1. The trachea of a large rabbit was tied, the abdomen and chest opened, and at the end of the second minute from the commencement of the experiment, the external iliac artery was divided ; a considerable quantity of dark blood flowed, but at the third minute it had almost ceased to escape. The heart continued contracting vigorously ; very small quantities of dark blood collected slowly every twenty seconds at the extremity of the artery. In five minutes all flow of blood had entirely ceased. The left heart contracted spontaneously fbr a very considerable period longer. I repeated this experiment with simi lar results."t Again, one of the variations of the experiment was as follows : " Experiment 3. A rabbit was asphyxiated by tying the trachea. The chest was opened. At the end of three minutes and a half no pulse could be discovered in the aorta. The left auricle was then opened, the blood contained escaped, and for a period of from one to three minutes, blood occasionally collected in very minute quantities, as though it gradually drained from the larger vessels of the lungs, but never, as often as the experiment was repeated, collected in quantity. The heart continued vigorous the usual period." " In general," says Dr. Kay, " the pheno mena of the cessation of motion in the left heart in asphyxia are these. A smaller quantity of blood is received into its cavities, and expelled time vigorously into the arteries. The ventricle meanwhile diminishes in size, as the quantity of blood supplied becomes less, until at length, although spontaneous contractions still occur in its fibres, no blood issues from a divided artery, and the ventricle, by contrac tion, has obliterated its cavity. After this, blood slowly accumulates in the auricle from the large vessels of the lungs ; and its con tractility continues for a very considerable period ."T Farther experiments by Dr. Kay show, that after the aorta of an animal has been tied, and after the muscles of its lower extremities have, in consequence, gradually lost all contractile power, that power is restored for a time by the injection of venous blood into the lower portion of the aorta ;§ and from these, and from some experiments by Dr. Edwards,* we learn, that the venous blood, though less powerful than arterial in maintaining the vital power of mus cles, is by no means rapidly destructive to it.