452 



NA TURE 



[September io, 1896 



tube was removed six inches from ihc animal. Those famihar 

 with this work will immediately see that, considering the 

 difference in size of the human body, a tube placed at that 

 distance could not possibly give the same result on a plate 

 or fluorescent screen. To begin with, we know that there 

 is a definite relationship between the distance at which the 

 photographic plate is removed from the object to be photo- 

 graphed on the one hand, and the distance between the object 

 and the Crookes' tube on the other. In other words, to get 

 anything like sharp definition it becomes necessary to remove 

 the tube to a considerable distance, which means of course loss 

 of power, and consequently more difficulty in seeing objects on 

 a fluorescent screen, and a longer time in exposing a plate. The 

 distance must vary in given cases, and experience, after careful 



Fig. 2. — Coin i^lp.^cted in gullet of boy aged six. 



experiment, in the present state of our knowledge can only 

 determine at what distance the tube is to be placed, although 

 ■we very often get a valuable suggestion by first examining an 

 object on the fluorescent .screen, and noting the distance of the 

 tube from the object. 



But another difficulty has now to be considered. Suppose we 

 wish to try to photograph the heart. The patient must be 

 placed on his face so that the organ may be as near the photo- 

 graphic plate as possible, and naturally the spine and other 

 organs which we do not wish to be photographed will be 

 between the object and the Crookes' lube. On the other 

 hand, if w-e wish to photograph the spine, it may be neces- 

 .sary to omit the tissues of the heart and lungs. A still better 

 example may be found in the case of the head, where the 



rays have to pass through the whole of the cranium, and yet the 

 surgeon may desire to photograph the inside of only one side of 

 the skull. Again, with renal calculus we do not wish to photo- 

 graph the intestines lying in front, nor the muscles of the back 

 behind. Fortunately the construction of the focus tube helps 

 us in this way, and in an earlier number of Nature of this 

 year I pointed out a method by which this might be accom- 

 jilished. The Rbntgen rays springing from the platinum anode 

 diverge from a point, consequently if we place the tube near the 

 right side of the head, and the photographic plate on the left, 

 the .shadows caused by those structures immediately next 

 the tube are so diffuse that they scarcely appear on the 

 negative, while a sufficient number of the rays still pass through 

 to photograph the part of the head which is in contact. By 

 carefully arranging the tube therefore, one 

 may photograph the heart, sternum and 

 ribsby the same method ; and if the patient 

 be placed on his back, lying on the sensi- 

 tive plate, these structures will be omitted, 

 but the spine will be photographed. We 

 can, also, by the same method photograph 

 any part of the skull at will. Considering 

 what has been said in the previous para- 

 graph, it might be here argued that, seeing 

 we are placing the tube near the body, 

 less power will be required ; but if we 

 reflect in the case of the abdominal, 

 thoracic, and cranial cavities, there is such 

 density of tissue to overcome that we are 

 more than ever in need of greater energy. 



Following out these indications, I made 

 a series of experiments and observations 

 upon the apparatus at my disposal, and 

 came early to the conclusion that more 

 powerful currents would be necessary. 

 Instead of measuring these in the usual 

 way by the length of the spark of the 

 coil, I placed Lord Kelvin's cell tester 

 and ampere-meter in the circuit with a 

 rheostat, so as to control the current at 

 will, and taking a large German coil, in 

 which the wires were thicker than the 

 English form, the currents were gradually 

 increased up to nearly thirty amperes. 

 The experiments were pushed to such an 

 extent that the focus tubes would not 

 stand the molecular strain, and for this 

 reason, at the instigation of Dr. J. T. 

 Bottomley, several strands of wire were 

 fused in the end of the tube bearing the 

 kathode, while the anode was made ad- 

 justable so that the platinum might be 

 removed at any distance from the kathode 

 until the maximum result was obtained. 

 There must be a relationship between the 

 amount of energy passed into the coil, on 

 the one hand, and the force coming out 

 from the focus tube after being transformed. 

 In other words, the coil is simply a trans- 

 former of a certain amount of energy which 

 gives rise to conditions within the tube, 

 which again give rise to X-rays. It was 

 evident I had pushed this to the limit of 

 the present make of tube. The question 

 will naturally here suggest itself to those 

 familiar with the suljject, Is it necessary 

 to use such currents, or could we not do with less energy 

 by properly economising the force in the transformer and 

 vacuum tube ? The question is a very proper one, as all 

 experimenters know that some lubes will give better results 

 than others with a certain amount of force passed through 

 a particular apparatus. This is yet to be settled, as well 

 as the questions involving the amount of current absolutely 

 necessary ; the best form of coil ; whether the coil itself 

 is the best kind of tramsformer : and lastly, and probably 

 most important of all, the conditions of the tube itself, 

 and they all afford examples of what has been previously 

 stated about the further need for physical research. What is 

 here meant by the above statements is simply : with the 

 apparatus as it stands at present, to get certain results, one is 



NO. 1402, VOL. 54] 



