Schleich's method consists in the injection into the substance of the skin of a solution of the alkaloids having anaesthetic property. The pressure exerted by the fluid is augmented by the aedema which ensues; hence it is known as "infiltration anaesthesia." Besides the local action of the anodyne, and the pressure on the nerve endings, absorption takes place, and a systemic impression adds to the local effect. The infiltration area is quite insensitive, and is marked by an urticaria-like eruption. The local anaesthesia lasts about twenty minutes, but the systemic effects continue during the usual time of a hypodermatic injection. The anaesthetic area can be extended in any direction, by successive injections. The strength of the solution may vary with the indications and the character of the tissue injected. Schleich employed three solutions containing cocaine, morphine, and common salt, as follows:

No. l. Rx Cocaine hydrochlor........................ ·2 = (gr. 3) approx.;

Morphine hydrochlor...................... ·025 = (gr. ½) approx.;

Sodii chlorid............................. ·2 = (gr. 3) approx.;

Aquae destillat. et steril................... ad 100 = f oz iv.

Add 2 drops of a 5-per-cent solution of carbolic acid.

No. 2.

Rx Cocaine hydrochlor........................ ·1 = (gr. l½) approx.;

Morphine hydrochlor...................... ·025 = (gr.⅛) approx.;

Sodii chlorid............................. ·2 = (gr. 3) approx.;

Aquae destil. et steril..................... ad 100 (f oz iv).

Add 2 drops of a 5-percent solution of carbolic acid.

The Schleich solution No. 3 has been found too dilute to have any decided effect, and is not any longer used on this side of the Atlantic. In fact, while the method is still used, surgeons do not restrict themselves to any specified formula. The main point is mixed anaesthesia, or infiltration anaesthesia, and the adaptation of this principle to comparatively weak solutions of the anodyne.

Solution No. 1 is intended to be used where the skin is inflamed or is highly sensitive. No. 2 is intended for ordinary conditions, and a very weak solution is used when extensive tracts of the skin are to be rendered insensitive by successive injections, whereby the danger of toxic effects is enhanced.

Eucaine has been proposed as a substitute for cocaine in this infiltration method. It is less depressing on the circulation and is less toxic, and the anaesthetic area is greater and the effect more persistent. Braun, however, in a recent elaborate investigation has shown that eucaine is distinctly inferior to cocaine for the purpose of local or infiltration anaesthesia. In comparing the various agents employed in this mode of anaesthesia, Braun found that the order of efficiency was first, cocaine, second, eucaine "B," third, eucaine "A." His final statement was that cocaine and eucaine "B" are the only substances to be employed in this way; that they alone cause local sensory paralysis without injury to the tissues. As respects the power of cocaine to lessen the sensibility of parts, the weakest solution having anaesthetic effect was recently ascertained to be 1 in 20,000, or, approximately, one grain of the hydrochlorate to two pints of distilled water.

The salt of eucaine usually employed is the hydrochlorate. This for internal administration may be given in solution, pill, or capsule, in doses corresponding with those of cocaine, over which it has the advantage that it has no toxic effects, causes no cardiac depression, and no nausea or vomiting. For ordinary purposes it may be applied topically in a 3-per-cent solution, in ophthalmic, nasal, or faucial affections, and in various minor surgical operations. Indeed, according to Schleich, eucaine may be substituted for cocaine in all of the applications made by the infiltration method, as in other respects.

Eucaine, "A" and "B."—Eucainae hydrochlorat. Eucaine is a modified cocaine, possessed of similar anodyne property, but without some ill effects that render cocaine undesirable. Eucaine "A" (alpha) is a benzoylamethylester in which for the ecgonin of cocaine is substituted another piperidine derivative. Among its advantages over cocaine are that it is less poisonous and is less injured by hot water, and has fewer after effects. Of the two eucaines, it is asserted that eucaine "B" is more soluble, less irritating, and possessed of equal anaesthetic property. It is preferred, therefore, for the production of local anaesthesia by Schleich's method. By Heinze it is advised that it should be administered in salt solution without morphine, according to the following formula :

Eucaine "B"...............................            ·1 (l·5 grs. approx.)

Sodium chloride............................            ·8 (12 approx.)

Distilled water.............................. ad 100· (f oz iv approx.)