Especially in injecting apparatus should a great amount of care be exercised about the selection. The greatest danger to be guarded against is corrosion, as all injecting fluids which are now in use contain more or less of either acids or metallic salts, all of which will attack and corrode, to a lesser or greater extent, the metals and other substances with which they come in direct contact. Any injector, therefore, so constructed as to be free from danger to its mechanism from the corroding effects of the liquids above mentioned, will be the one to be chosen. According to the statements above given, any part of an apparatus which is required to operate with a certain degree of nicety must be kept from the corrosive effects of the fluids, and this result is to be gained only by the peculiar construction of the apparatus. In the greater part of the injecting pumps now manufactured and in use in this country, the body of the pump, which contains the working part of the apparatus, is also filled with the liquid while in use; and, therefore, this part, which ought to be protected from injury, is constantly immersed in the strong corrosive solution during all the time that the injector is being worked. The result of this constant corroding action upon the apparatus will soon show itself in the working of it, and constant repairs will be found necessary to keep it in order or in a state of comparative effectiveness. It must be well remembered, that upon the working of the apparatus depends, to a great extent, the good or poor success of embalming; also, that upon the manner of using an apparatus, of whatever description it may be, the length of its duration and its effectiveness will be in the same ratio. The automatic apparatus of Girard, for injecting purposes, is a marvel of simplicity and durability; there is no piston or force pump, which is liable at any moment to get out of order; no valves, which will wear out by friction, or leak from the effects of the liquid used. The force used in ejecting the fluid is that of a gas, highly antiseptic in its nature, and which, being generated inside of a cylinder, saturates the injecting fluid (itself an antiseptic solution), and by its expansive force propels it into the arteries of the body. All the appliances necessary to the perfect working of the apparatus are condensed into a small compass. The amount of gas generated can be increased or diminished at will. A pressure gage indicates the force of expansion acquired by the gas. A glass tube, similar to the water tube in use on some boilers, and with a graduated scale attached, shows both the amount of liquid used and also the quantity remaining in the apparatus; while a relief-cock insures safety to the operator against too rapid an accumulation of gas.