192 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
Some diseases cause fairly characteristic changes in bone, but these 
are in the minority. The more experience the observer has the more 
he realizes that a host of different conditions can produce identical 
pathological and, therefore, identical radiological changes. A good 
example of this is leprosy. Many years ago an author reported “char- 
acteristic” atrophy of the terminal phalanges as a fairly early sign 
of this disease. On studying cases of nerve disease of other types, 
and of obliterative or spastic vascular diseases of various types, it 
was found that quite identical changes occurred in many of them. 
Phosphorus poisoning causes changes in the jaw bone similar to those 
of infection and of radium poisoning. Thus, it is important to main- 
tain reserve in accepting reports of new or “characteristic” findings 
in disease. 
One interesting finding in roentgenograms of children’s extremities 
is that seen in lead poisoning. Children who have licked the paint off 
of their toys or pens sometimes develop signs of joint disease or leg 
weakness. If they have been following this dietary indiscretion for 
some time, the growing ends of long bones will show dense lines due 
to actual deposit of lead salts therein. 
The roentgenologist is required to have a general knowledge of the 
development, anatomy, and pathology of the teeth. Satisfactory ex- 
amination of the teeth requires careful technique and even more 
careful interpretation. Without the latter, early abscesses at the roots 
of the teeth, early areas of caries or decay in the crowns, and similar 
processes may be overlooked. 
The value of a consultant specialist is almost nowhere better seen 
than in certain cases of dental radiography. The dentist or family 
doctor is apt to look at such films with his thoughts concentrated 
purely on the dental structures and innocently may neglect a malig- 
nant growth in the adjacent bony mandible, a lesion which an expert 
in the field of X-ray interpretation would be apt to detect readily. It 
is not suggested that ability in such interpretation is confined exclus- 
ively to the roentgenologist. Any person, professional or otherwise, 
can learn how to interpret films of certain parts of the body after a 
fairly short period of training. However, the human tendency is 
to concentrate on the matters in which one is most interested and 
te overlook other data, even though such are quite apparent on 
retrospect. 
Normal joint cartilage casts no distinguishing shadow in roent- 
genograms so routine Roentgen methods are not of much value in the 
early diagnosis of many types of joint disease. However, “soft- 
tissue” films of joints, and films made following intra-articular injec- 
tion of air do provide valuable diagnostic information in many cases. 
Roentgenograms are of considerable value in the differential diag- 
