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.
This last danger need scarcely be apprehended, as, after the pressure gage indicates the force of expansion required, the further generation of the gas can be entirely stopped, until the vacuum created by the outflow of liquid needs to be replaced by a new supply of gas. For it is a fact well understood, that the force of expansion of the generating power decreases in the same proportion as the volume of the liquid is diminished, thereby causing a greater vacuum in the apparatus.
The inside of the apparatus is thickly coated with lead, as that metal is not sensibly acted on by either muriatic or sulphuric acid, except at very high temperatures.
The jet or stream of liquid can be regulated by a screw cock, attached to the neck of a metallic tube reaching to the bottom of the apparatus, inside, and provided at its inner extremity with a perforated bulb, which, acting as a filter, prevents any impurity or sediment from finding its way into and stopping the circulation of the fluid through the arterial system; at the same time it prevents any excessive amount of pressure upon the rubber tube five or six feet in length, which is connected with the delivery tube outside, and at the end of which the nozzle is attached.
The nozzle or cannula itself is a very important part of the apparatus, and is of a peculiar shape; it consists of a thin copper tube about eight inches in length and a little over an eighth of an inch in diameter; it is to be inserted at full length, or nearly so, into the artery to be injected, as by doing so it meets a point where the walls of the artery are strengthened by the surrounding tissues.
The shape of the apparatus is that of an elongated cylinder, rounded off at both ends, resembling somewhat a soda fountain; it stands upright, upon four curved legs about four inches in height, and possesses a symmetrical and substantial appearance.