186 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
systems of the human body. However, it is timely at this point to 
acknowledge the debt of roentgenology to members of the specialties 
outside of its own field, physicians who have contributed greatly to 
the refinements of many techniques in diagnosis as well as treatment. 
The reader should know that there are now “national qualifying 
boards for specialists.’ These boards examine eligible graduate 
physicians and certify those who pass successfully. At the present 
time there are boards in the following branches of medicine: 
1. Anesthesiology. 9. Pathology. 
2. Dermatology and syphilology. 10. Pediatrics. 
3. Internal medicine. 11. Plastic surgery. 
4. Neurological surgery. 12. Psychiatry and neurology. 
5. Obstetrics and gynecology. 18. Radiology. 
6. Ophthalmology. 14. Surgery. 
7. Orthopedic surgery. 15. Neurology. 
8. Otolaryngology. 
X-ray diagnostic methods involve first and foremost intelligent 
use: one case may be diagnosed quickest without X-rays at all; the 
next may need only flouroscopy; the third, fiuoroscopy, roentgeno- 
grams, and special-section techniques; the fourth may require re- 
peated roentgenograms. Only a trained physician knows the correct 
answer to these questions: only a trained physician can be economic 
in the exposure of your tissues to a radiation known to be noxious. The 
wise layman selects his physician-radiologist according to his expe- 
rience or ability, and not according to the newness or extent of his 
equipment. In assessing the value of a roentgenogram it is important 
to remember that it is just a shadowgraph and not a true photograph 
and as such is subject to erroneous interpretation. Furthermore, the 
roentgenogram is a projection on a flat surface of everything on every 
plane between the X-ray tube and the film. Thus it is desirable that 
the interpreter familiarize himself with the projected appearance 
of normal structures of various shapes. Multiple views, preferably 
at right angles, usually are essential; stereoscopic roentgenograms 
frequently are necessary. The examination of moving parts such as 
the stomach, heart, or diaphragm frequently requires fluoroscopy 
as well as multiple films. 
There are many shadows in roentgenograms of healthy persons 
which cause errors in interpretation. These include the normal 
epiphyseal or growth line in bones (often mistaken for a fracture), 
the overlapping of a bony margin, or the slender canal of the artery 
to the bone. The existence of a congenital fissure or cleft also may be 
mistaken for a fracture. Calcium deposits are fairly common in 
various tissues; they are normal findings in rib cartilages, laryngeal 
cartilages, and certain other areas, but occasionally they are mistaken 
for tuberculous lesions, foreign bodies, and so on. This is one of the 
