March, 1911. 



KNOWLEDGE. 



83 



photograph, as it is sometimes erroneously termed. 

 The propert\- of arresting the passage of the X-rays 



ood radiogra})h of the 



Figure 3. A Jtt Break. 



and thus casting a shadow is jiurelx- a question of the 

 atomic weight of the elements that luake up an\- 

 substance. Speaking generalh', substances of 

 vegetable and animal origin, except the bones, are 

 ver\- transparent. With the exception of aluminium, 

 all the metals in common use are more or less 

 uniformh- opaque. Calcium having an intermediate 

 atomic weight is seiui-transparent. and as lime salts 

 enter very largel\- into the structure of most living 

 organisms, the X-rays are verv valuable in stud\-ing 

 their normal structure as well as tracing departures 

 from the normal, whether from disease or accident. 

 An}- inequalities in thickness are registered on the 

 screen or plate, and so accurately is this done under 

 favourable conditions that the details of structure 

 can often be made out : a 

 hand or foot shows this ver_v well. 



Some verv interesting discoveries ha\e been made 

 in this way regarding the internal structure of shells, 

 and the Ravs have been used in examining oysters for 

 the presence of pearls. If no pearls are present the 

 oj'ster is returned to the sea, which is presumably an 

 advantage to the oyster. In a like manner electrical 

 cables are examined (see Figure 1), both for the 

 continuit}' of the conductor as well as to see that it 

 maintains its proper relation to the other members 

 of the system. The modern electric cable is in 

 many instances a very highl}- specialised structure, 

 that has to stand very severe strains both mechani- 

 cal and electrical, and, as an apparently small fault 

 may give rise to very serious trouble, the final 

 inspection has to be carried out with the greatest 

 care before it is passed as fit for service. 



With regard to the medical and surgical uses of 

 the X-ra}s, most people are inclined to think that 



the examination of fractures and the detection of 

 foreign bodies within the human organism constitute 

 the main field of their usefulness. These are, of 

 course. \ery important applications, and ones that 

 count for nuich in hospital practice particularlw but 

 they do not by any means constitute the whole. An 

 ordinary simple fracture occurring in the shaft of a 

 long bone such as in the middle of the upper arm, 

 can be dealt with quite satisfactorily, whether 

 examined liy the X-rays or not : but the surgeon 

 who attempts to deal with a fracture close to, or 

 invobing a joint, without having it properly 

 examined b\- this method, takes a risk to his patient, 

 as well as to his own reputation, that is not justifiable. 

 An instance of this is shown in the accompanying 

 radiograph (see Figure 6) ; this injured wrist was 

 declared to be a severe sprain and treated as such. 

 Fortunately the patient decided to come to the 

 hospital, where it was X-rayed as a matter of 

 routine. This shows that the bone is not only 

 broken in at least three fragments, but that one 

 of the lines of fracture enters the wrist joint. The 

 fact that there was no displacement of the frag- 

 ments led to the erroneous diagnosis being made, 

 and had this been treated in the ordinarv wav a 

 stiff wrist joint would have resulted almost certainl}-. 

 In the early da\"s of the X-ra\s their use was 

 almost entirely confined to stricth' surgical cases ; 

 now adays the method is used almost as much for the 

 investigation of medical cases, such as disease of the 

 respiratory organs, the heart and great blood vessels. 



y.V the courtesy of Messrs. XcwUn &> Co. 



Figure 4. A Dipper Break. 



