X-Rays, Apparatus and Methods Page 12

into the operating room in a condition of more or less nervous collapse to begin with is obvious.

(f) Strain on Tube. — It has been argued by advocates of the "high-frequency" coil that it is much less hard upon the tubes. Our own observation has been just the reverse of this, and has satisfied us that the wear and tear is very much less with the induction coil.

(g) Results. — Although we have diligently examined, we have yet to see results obtained by any form of apparatus superior to those made in Philadelphia by Dr. Goodspeed, of the University of Pennsylvania; Dr. Stern, of the Polyclinic Hospital; ourselves, and many others who might be mentioned, and this either as regards detail, penetration or quickness of exposure. Indeed, we may say that we have never seen results obtained with the Tesla coil that are equal in any of the above respects to the results just referred to.

The Tube. — Many forms of tubes have been suggested. With practically no exception, all tubes now in use employ as cathode a concave aluminum disc, whose center of curvature is at the center of a small platinum plate (¼ to ½ square inch in area) the plane of the plate being inclined to the normal from center of the concave cathode. This platinum plate is sometimes made the anode — sometimes the anode is a separate plate or wire elsewhere in the tube. This form of tube is known as the "focus" tube, the cathode rays being focussed upon the platinum plate, which then becomes the active source of X-rays. In the double-focus tube we have two concave cathodes at opposite ends of the tube, the platinum wire reflector being in the form of a wedge with a side presented to each of the concave cathodes.

In the use of the tube everything depends upon the vacuum, X-rays seeming to be of a heterogeneous character, just as are light rays, their quality varying with the degree of vacuum. The higher the vacuum the more penetrating power the tube has, hence it is well to select tubes and use different tubes for different purposes. A tube of extremely high exhaustion is best for working through the body, but with forearm, hands, feet, etc., such a tube has