The art of sciagraphy, more nearly, as every month passes, becomes developed by means of improved apparatus, screens, photographic plates and other elements which at present are only dimly predicted. Nevertheless, how can a better sciagraph of bones, showing their thickness and porosity, be desired than that reproduced on page 177, and taken by Prof. Arthur W. Goodspeed, and representing a club foot of a child? In the race to excel in this new art, no one, to the author’s knowledge, has surpassed Prof. Goodspeed, of the University of Penn., considered jointly from the standpoints of _priority_, _superiority_, _quantity_ and _variety_. Dr. Keen, L.L.D., Professor in the Jefferson Medical College, of Philadelphia, stated (_Inter. Nat. Med. Mag._, June, ’96) that Prof. Goodspeed “has far eclipsed all others in these most beautifully clear sciagraphs.” 210. A book could be filled with the numerous cases of diagnosis by X-rays showing the utility. In closing this chapter, let it suffice to mention some of the sources of literature relating to this subject directly or indirectly: location of shot (by Dr. Ashhurst, Phila.) in lady’s wrist, not located by other means. Dr. Packard’s case of acromegaly; Dr. Muller’s (Germantown) location of needle in boy’s foot; cause of pain not before known; needle subsequently removed; a perfect thorax, or trunk, by Prof. Arthur W. Goodspeed, University of Pennsylvania; Thomas G. Morton’s (M. D. Pres. Acad. Surg., Phila.) application to painful affection of the foot, called metatarsaligia. All of the above noticed in _Inter. Med. Mag._, June, 1896. Case of a burned hand with anchylosis of the fingers, by W. W. Keen, M.D., L.L.D. Bacteria not killed by X-rays. Normal and abnormal phalanx distinguished. Fracture and dislocation sometimes differentiated by X-rays. _Amer. Jour. Med. Sci._, Mar., ’96. ------------------------------------------------------------------------ CHAPTER XIV THEORETICAL CONSIDERATIONS. ------- Before attempting to discuss the facts now known in regard to the Roentgen phenomena, it is well to review briefly the known ways in which radiant energy may be transmitted. By radiant energy is, of course, meant energy proceeding outward from a source and producing effects at some distant point. There are two well understood ways in which energy may be transmitted,—first, by an actual transfer to the distant point of matter to which the energy has been imparted from the source, as in the flight of a common ball, a bullet, or a charge of shot. In this mode of transmission, it is evident that the flying particles, assuming that they are subject to no forces on the way, will move in straight lines from the source to the distant point. They constitute real rays, diverging from the source; an obstacle in their path, would, if the radiations proceeded from a point, cast a shadow with sharply defined edges.