PKOGRESS IN EADIOGRAPHY. 155 



number of interruptions per second in the current which forms the 

 electric discharges in the tube, the image is quickly or slowly formed 

 on the photographic plate. 



To make a radiograph when one has the proper materials at hand 

 is a jDhysical experiment which any college student can perform as 

 easily as he can bring about a simple chemical reaction. But as this 

 student would be utterl}' incapable of making a quantitative or quali- 

 tative chemical analysis, no more can he carry out a rational radio- 

 graphic research to determine even the simplest fracture. This com- 

 parison is not an idle oue, for just as a man is not a full-fledged 

 chemist when he knows how to make a single kind of analysis, a man 

 is by no means a really competent radiographer because he can get a 

 good radiograph of a fracture of the arm or leg. 



There are as many different methods of radiographing as there are 

 different cases to be treated, and the processes vary with the nature 

 of the subject. A broken bone in the hand is not approached in the 

 same way as is a fracture in the foot ; the thigh is a good deal more 

 difficult to radiograph than the forearm; and a break in the neck of 

 the feunir, for instance, is one particularly difficult to determine. 

 Certain simjile fractures almost reproduce themselves — that is to say, 

 despite the incompetence of the operator — while others, where the 

 bone is not nnich displaced, are exceedingly elusive. 



Radiography, however, does not concern itself entirely with l)roken 

 bones; it reveals innumerable other organic alterations. Before 

 taking up any of its principal applications in surgery and medicine, 

 let us glance for a moment at its utilization in locating foreign sub- 

 stances in the body. 



The human body would seem to be in little danger of accidental 

 l^enetration by extraneous substances, but as a matter of fact these 

 penetrations are not uncommon, especially in the larger cities. In 

 Paris, for instance, hundreds of people have needles, pins, bullets, 

 grains of lead, pieces of money, or metallic splinters extracted from 

 their muscular tissues, intestines, stomach, oesophagus, eyes, and even 

 from the brain itself, which is, contrary to the general opinion, easily 

 explored by modern methods without fatal results. 



All searches for foreign substances in these various parts of the 

 body require a most exact localization, for it is necessary to know 

 just where the object is before operating with scalpel and forceps. 

 To understand the complexity, let us imagine the patient is the victim 

 of a footpad, brought unconscious to the hospital. He has been shot 

 in the chest; the womid is ])lain enough. In the hoi)e that tlic ball 

 has not penetrated far the surgeon ])r()bes, but finds nothing. The 

 bullet has gone deep; possibly it is near the heart or some other vital 

 organ. In such a case it would be dangerous to grope blindly with 

 the proble, and a radiograph localization becomes necessary. 



