In order to conduct a narcosis scientifically one must know the signs of sufficient anesthesia and the signs of awakening.

The respiration is studied by watching the movements of the chest or abdomen, by placing the hand in the vicinity of the nostril to feel the respiratory current of air, or, best of all, for the respiration is rarely noiseless, by listening to the breathing. The quality of the breathing is noted. The faintest indication of a snoring respiration means that the surgical degree has been reached. Any change in the quality of the breathing compels the questions “Has the patient escaped from the proper surgical plane?” “Is the anesthesia too deep or too superficial?” or “Is the change simply a respiratory reflex induced by the surgeon’s manipulations?”

The color of the ear is a most useful guide. This does not hold good of the color of the forehead. The forehead in some individuals becomes cyanotic with slight changes of posture. The ear is not so subject to postural influences and is therefore a less misleading indicator of the venous condition of the blood. Even a slightly bluish tinge of the ear demands attention. Usually, crowding is the cause, and a little more air allows the normal red flush to return. Slight pallor developing during the course of the narcosis should always be regarded as a danger sign. It means that the patient is in profound anesthesia, and that the heart is threatening collapse. The mask should be removed promptly and the patient allowed to breathe pure air. As long as the pulse is not weak or irregular one need not worry about the outcome.

There are some advantages in choosing the temporal pulse as the guide, instead of the radial pulse, which is ordinarily followed; occasionally the temporal can still be felt when the radial has become impalpable. The pulsation of the temporal artery is best felt by placing the index finger flat over the tragus into the depression at the root of the ear. The pulse is important because it tells how the heart reacts towards the anesthetic and the surgeon’s manipulations. The frequency is not very important. Exceptionally, it may be 120 or 130 during the greater part of an anesthesia without vital significance, if the quality is good. A diffuse and weakening pulse is a signal that the narcosis is too profound and that the heart is in danger of collapse. A somewhat irregular pulse may immediately precede or accompany the act of vomiting, and it is not a cause for alarm.

Accessory to the respiration, color and pulse, but of lesser significance, are the pupil, the cornea and eyelid, and the secretions.

In patients who have not received morphine before narcosis the pupil is, as a rule, a guide of some importance. If the pupil is narrow, examination of its reaction to light is generally superfluous. A wide pupil, however, often means one or the other extreme of narcosis. A wide pupil which reacts promptly to light indicates superficial anesthesia; the patient may need more of the anesthetic. A wide pupil which reacts to light sluggishly or not at all means that the danger line has been overstepped; the anesthesia is too deep; the patient must have air. Without knowledge of the reaction, every markedly dilated pupil should be looked upon as prognostic of danger.

To touch the cornea repeatedly with the finger for the purpose of obtaining the corneal reflex, is a bad habit. The reflex can be tested just as satisfactorily by shifting the eyelid gently across its surface.

A point worth remembering is that in the morphine-anaesthol (or morphine-chloroform) anesthesia the corneal reflex may remain quite active, while with ether it soon becomes feeble or extinct.

A useful indicator of the degree of muscular relaxation is, I believe, the tonicity of the eyelid. The usual arm test is very misleading. Flexing the elbow once or twice may give the impression that the muscles are thoroughly relaxed, and yet, on repeating the manipulation five or six times one may be surprised to obtain a sudden, powerful contraction of the biceps, showing that the patient is still not fully under the influence of the narcotic.

Normally the upper lid has a certain tonicity. If it is lifted gently by means of the superimposed ball of the finger it springs back to its natural position promptly. When the patient is fully under the influence of the anesthetic, this tonicity is partly or completely lost and the lid returns sluggishly to its natural position, or not at all. The patient can sometimes be kept in a proper surgical plane by giving a few drops of the anesthetic each time as the tonicity returns, and ceasing when relaxation of the eyelid is obtained.

When the patient is under anesthesia to the surgical degree the activity of the salivary, sweat and tear glands ceases. The accumulation of mucus in the mouth, the appearance of a tear in the eye, beads of perspiration on the brow all mean that the anesthesia is becoming superficial, that more anesthetic is "Individual Idiosyncrasy" required. It is worth bearing in mind that these indicators of the depth of narcosis do not, in all individuals, react in exactly the same way. While initiating the narcosis the anesthetist can get his bearings in regard to this point, and watch for any individual idiosyncrasy which may exist.

It is unsafe to concentrate the attention on one sign, lest the general aspect of the patient be overlooked.

The anesthetist watches constantly the rhythm and quality of the breathing, the color of the ear and the character of the pulse. From time to time, only as occasion demands, he refers to the accessory signs for confirmation. Should he, at any time, be in doubt about the depth of the narcosis, the first step is always to desist from giving more of the anesthetic until he has regained his bearings or the signs of awakening are recognized.