_Injections_, made immediately after connection, even with the most splendid syringes, are not of themselves sufficient; they always can come too late. Dr. HINZ has invented a small syringe with an indiarubber ball at each end of a tube, recommended by Dr. FISCHER-DUCKELMANN, to inject a spermicide liquid, which is warmed, at the moment of the emission. This syringe is called _Facilitas_, but it is neither easy nor secure. With these syringes the liquids mentioned in the following chapter may also be used. For the success of any of these methods, it is indispensable that the wife should be acquainted with the position of the mouth of the womb. INJECTIONS. Injections are an essential point of the sexual hygiene of the wife; but they are not sufficient alone: they complete the other preventive methods. As injection, any acid solution may be used; for instance, _vinegar_ with equal parts of water, or a solution of 1 per cent. of citric or tartaric acid, etc. Any astringent solution, which is also useful in the case of white discharges: _sulphate of zinc_ or _alum_, of either 1 per cent. (a dessertspoonful of the powder in a litre or in a large bottle of water). Or _corrosive sublimate_ (perchloride of mercury), a decigramme dissolved in a large bottle of water. This last solution is also very powerful against venereal contagion; but, if too frequently employed, it may prove poisonous. Solutions of copper or nitrate of silver may be used; but these solutions stain the linen. Copper, if long used, is poisonous. Now, what syringe should be used? The simplest instrument is the _glass syringe_, not curved, of large size (containing 60 cmc. of liquid), which costs 25 cents. The solution is poured into a cup and drawn up into the syringe; the piston should be so carefully fitted that no fluid will escape when the syringe is held downward. The most efficacious method of using the injection is to lie on the back, on a vessel receiving the fluid, the thighs drawn up and separated. The syringe is pushed up into the vagina as far as possible, and then this piston is rapidly pushed down; when this has been done, the syringe is moved from right to left, in order to wash out all the folds of the vagina. Other instruments may as well be employed if it be only a syringe with a long tube, that it may reach all vaginal folds—the _clysopompe_, which acts by means of a spring; the _clysior_ or oblong bulb, with a tube at each end; the _irrigator_, which is hung up on a nail high up on the wall. These latter instruments require a much greater quantity of the solution than the glass syringe requires. Therefore the fluid, almost a litre, should be warmed when the weather is very cold, or when the woman is very sensitive.