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pressure of the blood, and to contract with more strength than before when the pressure is acting upon its walls and opposing itself to their contraction. The apparent paralysis must depend on this cause: the vaso-motor nerves are paralysed, inasmuch as all the vessels of the body are dilated; their increased capacity retains the blood, now no longer returned to the heart, which becomes bloodless in a secondary manner. Compression of the abdomen, or ligatures to the upper and lower extremities, produces a compensation for the increased capacity of the bloodvessels, and in this way the circulation becomes more normal, while before it had suffered, not through paralysis of the heart, but from paralytic dilatation of the peripheral vessels.
As regards the comparative value of ether and chloroform, Professor Schiff continues:-" Our own experiments bearing on this argument enable us to say that in more than three thousand cases we have adopted etherisation with a view to preserve the life of animals, and that with the few exceptions indicated elsewhere (Memoir on the Laryngeal Nerve), not a single case of death occurred. On the other hand, chloroform has cost us a considerable number of animals when I have wished to push anæsthesia to its ultimate stage.
Our experiments confirm more and more that in etherisation the pressure of the vessels maintains itself to a height almost normal and always compatible with the continuance of life even after the cessation of automatic and the substitution of artificial respiration, so that the mere continuance of breathing gives us a safe warranty of the vitality of the individual. Often in experiments made with this view, we have seen that at the moment of the cessation of automatic breathing the circulation was still in so normal a state that the commencement of asphyxia indicated still the asphyxic height of vascular pressure as measured by the manometer; that is, instead of falling before death, the pressure rose through the accumulation of carbonic acid, which, as is known, is an irritant of the vascular system and of its nerves.
When, after the cessation of breathing, one at once applies artificial respiration with air that is passed over a stratum of ether, so that etherisation is still kept up, one is able, by regulating the quantity of ether that is mixed with the air, to continue for hours the etherisation of the animal, which no longer breathes
spontaneously, without the pressure of the blood being notably diminished, and without danger to the life of the animal, which one can always resuscitate by introducing pure air into the lungs.
"It is true, however, that the pressure of the blood always diminishes slightly, so that after two hours it may have fallen, for example, from 120 to 80 millimeters; but such a fall is not prejudicial to life. One is able in these experiments to regulate with facility the quantity of ether, commencing with a low temperature of the vessel that contains it. If one finds that the animal shows a ready tendency to recommence certain automatic respiratory movements, Wolf's bottle, which contains the ether, and is connected with the bellows and manometer by means of india-rubber tubes, is brought rather nearer to the body of the animal so as to increase the heating effect.
"It is otherwise with chloroform. In animals in which, under the influence of this agent, the pressure of the blood has been examined with the manometer, one finds that the pressure is already considerably lowered before automatic respiration has ceased; and we have frequently seen the pulse disappear almost entirely in the manometer, whilst the pressure fell to 25 or 30 millimeters, and the dog still breathed spontaneously.
"In dogs in which one employs artificial respiration from the commencement, causing the air to pass through a bottle containing chloroform, so that in entering the lungs it is but feebly loaded with this agent, we have seen the pressure, sometimes immediately, sometimes after a longer period, lower itself almost to zero, while the extremely weak pulse which the manometer recorded has also ceased soon afterwards, the respiration being continued as at the beginning of the experiment. It is therefore certain that in these cases it was not the cessation of the respiration, nor its weakening, that killed the animal. This becomes yet more evident through the experiments in which, after the cessation of vascular pressure, when the pressure was that of blood almost at rest, one suddenly replaced the respiration of chloroformised air by normal air without being able to save the animal.
"After a few forced inspirations one sometimes sees the automatic breathing of the animal recommence. This may be up to
two, four, and, as in one case, ten automatic inspirations; but the pressure of the blood does not rise, and the dog dies through cessation of circulation.
"Fortunately things do not always go thus. It is possible to find that a very limited quantity of chloroform mixed with the air may maintain a state of apparent death without any automatic respiration, and with an extreme fall of arterial pressure that yet admits, after half an hour's continuance of chloroformisation, of the re-establishment of life on pure air being introduced. But the keeping the animal alive in such an experiment is always uncertain: we cannot make sure, as with ether, that the animal will be revived. We are never able to say, and this is a great point, what the limit of chloroform is in the inspired air, which affords us a certainty of the animal being restored."
These results of Professor Schiff's labours, which I have frequently seen demonstrated by him, have so impressed me with their importance that I would express a hope that the questions they involve may undergo a fresh discussion. I have translated his own words with a view to give fuller weight to his opinions. He considers that chloroform should be banished from practice as an anesthetic agent, except in cases in which extraordinary resistance to the effect of ether shows itself, in which instances it might be allowed to mix a little chloroform with it in order to produce the commencement of anesthesia, which should afterwards be continued with pure ether.
As regards the precautions during the use of ether which Professor Schiff points to in referring to his memoir on the laryngeal nerve (" Ueber die angebliche Hemmungsfunction des Nervus Laryngeus Inferior," published in Moleschott's Untersuchungen, 1867), they are too important and interesting to be passed over. The paper containing them was written a short time after the publication of the discovery of Rosenthal that irritation of the superior laryngeal nerve has an inhibitory influence on the respiratory movements. After having shown that in rabbits, guinea-pigs, frogs and toads, many sensitive nerves of the anterior part of the body, and in some cases all the sensitive nerves of the skin, have an inhibitory influence on the respiration and on the heart's action when they are slightly irritated in a continuous manner (by mechanical means),
and that in this respect the superior laryngeal nerve has not an exceptional position, but shows only a quantitative difference, the author mentions that in normal dogs and cats he did not find the same effect from irritation of sensitive nerves; but that during the return of these animals from a very deep etherisation or chloroformisation, while the respiratory impulse is weak but regular, he did not find it difficult to show this inhibitory influence in many sensitive nerves of the anterior part of the body and over the middle line of the back along the course of the vertebral canal, onthe pulse and respiration.
The animal is etherised or chloroformised until respiratory movement has quite ceased; then artificial respiration, by interrupted compression of the abdomen and chest, is employed. Under ether the recovery is certain; and when the animal begins to breathe automatically, but still weakly, there is a moment in which any strong mechanical irritation of the nerves above indicated produces a new and a more persistent asphyxia; the diaphragm is relaxed, and it seldom happens that the animal is recalled to life by a return to artificial respiration. The persistence of this new species of asphyxia is now explained by Professor Schiff's more recent researches on the subject, in which the mechanical irritation of a posterior spinal root, previously laid bare, produced paralysis of the circulation. This is a reflex paralysis of the same kind as that which Ludwig and Cyon produced in a slighter degree in normal rabbits by the irritation of the nervus cardiacus longus,
This experiment can be made only during a short period on the return of the animal from the highest degree of etherisation or chloroformisation; and when this very brief period is passed, irritation of the nerve has no longer the influence now pointed out on the respiration, but acts in an inverse manner on the pulse, increasing its strength and at the same time the pressure of the blood. In connection with this phenomenon Professor Schiff observes that, considering the analogous manner in which sensibility is reflected in the spinal marrow of these animals and of man, this experiment affords a warning of much importance to surgeons, not to continue an operation immediately on a patient's recovery from the excessive action of anaesthetics, but to wait until respiration has been energetically restored, other
wise a new and generally fatal asphyxia may be produced. In his last and not yet published experiments on this subject, Professor Schiff killed some dogs in the first period of return from asphyxia produced by ether only, by raising with a tentaculum one or two posterior roots of the dorsal nerves; while in other dogs prepared in the same way, in which the same operation preceded the division of these nerves, in a somewhat more advanced period of the return of respiration, that function continued in its regular progress up to the time of consciousness being restored.
Before concluding, it may be of interest to many to learn that the Laboratory of Physiology in Florence, of which Professor Schiff is the illustrious head, is a public establishment on a very large scale, where every kind of apparatus by means of which physiological science may be advanced is collected; while the courtesy of the Professor holds out every inducement to scientific men to visit the institution, as well as to witness and join in the investigations which are being constantly made within its walls.
FLORENCE, Feb. 25, 1874.