1897J MICROSCOPICAL JOURNAL 379 



wLich is exactly at right angles with the first. The pins 

 are again brought into use, and the table, patient and 

 fluorometer, together, brought into parallelism with tln^ 

 rays, the tube having now heen placed over the patient, 

 as shown on the opposite page, instead of the side. The 

 position of the foreign object again, with reference to 

 the points on the cross-section of the subject and witli 

 reference to certain points on the fluorometer, is at once 

 charted by the aid of the meshes of the metallic grating. 



Necessarily, the foreign object must be situated at the 

 point where the two lines coincide, the distortion caused 

 by position, also the distortion caused by the angle of 

 the ray having been eliminate. Where that point is, 

 can, of course, be at once ascertained by measurment on 

 the surface of the body. 



In the case of a bullet in the brain cavity elements of 

 uncertainty of location, having in view the desirability 

 of a possible operation for its removal, become very grave. 

 A very slight variation of the position occupied by the head 

 will produce a distortion which would preclude success- 

 full exploration. By means of the fluorometer the position 

 of a foreign object in the brain cavity is ascertained with 

 precision exactly as in the case of the body already given: 

 it becomes merely a matter of cross-sections and surface 

 measurements. 



In the case of a bullet in the shoulder there is the pos- 

 sible difficulty of distinguishing a foreign object by ex- 

 amining the shadow thrown transversely to the body. 

 With this system, however, the difficulty vanishes. Bar- 

 ing the shoulder, the a}»pliance is fixed directly over the 

 center of the foreign object, it having been disclosed by 

 superficial view. The body is then brought into such a 

 position that the appliance shows only the characteris- 

 tic thin vertical line on the field of the fluoroscope. A 

 line of India ink is then drawn across the shoulders to 

 indicate the cross-section obtained. Then removing the 



