268 



SCIENCE-GOSSIP. 



hence the smell ; ferricyanide is again formed, which 

 combines with the protochloride of iron also present, 

 hence the blue precipitate, and the persalt is left as 

 a brown precipitate. As sea-birds' eggs are the only 

 ones giving a red precipitate and producing the sul- 

 phurous smell, the truth of the above theory admits 

 of little doubt. Its importance lies not only in the 

 demonstration of the presence of sulphur, but also 

 because it proves that perchloride is really formed, 

 and iron therefore must have existed in the shell. 

 Even if sulphur was present in some other form than 

 sulphide of iron, the result would be the same, as the 

 acid would decompose any substance with which it 

 was in combination. These results, certainly, in- 

 directly increase the probability that the green in 

 the eggs of some sea-birds is caused by sulphate 

 of iron. There is nothing inherently improbable 

 in the existence of sulphur on the shell of an 

 egg, seeing what an important constituent it is of the 

 contents. 



Regarding the comparison between the barn-owl 

 and the kestrel, the owl is a noctunral bird, the 

 kestrel is not. Therefore the remarks I have already 

 made apply to the former, whilst as the kestrel often 

 lays its eggs on the ground and in other exposed 

 positions their prevailing red-brown colour is ex- 

 tremely useful. I agree it would be better to place 



the owls in Class 5 ; in fact, they bear the same 

 relation to this class that the petrels and shear- 

 waters do to Class 3. I do not, however, regard the 

 subject as by any means settled, and shall continue 

 my experiments, chiefly with a view to discover the 

 substance which partly disguises the iron before it is 

 heated. 



Since writing the above I have found another very 

 satisfactory proof of the presence of iron in the pig- 

 ment, from the fact that the characteristic blue pre- 

 cipitate can often be obtained, without heating, by 

 first pouring on either hydrochloric or nitric acid, 

 and then adding a very small drop of potassium ferro- 

 cyanide. This method succeeds best with gulls' or 

 terns' eggs, and would seem to imply a comparative 

 scarcity of the disguising substance to which I have 

 alluded. The nitric acid, when first poured on, forms 

 a bright scarlet solution, disappears when allowed 

 to dry, but leaves the colour darker than before. 

 The nitric acid probably both peroxidises the iron 

 and partly destroys the disguising substance. Care 

 must be taken, when this acid is used, that the green 

 it always forms with the ferrocyanide does not dis- 

 guise the blue. This can be avoided by not using 

 too much of either. 

 Norman Court, 



Southsea. 



RADIOGRAPHY. 



By James Quick. 



(Continued from page 231.) 



IN the preceding articles of this series, Radio- 

 graphy has mainly been considered from the 

 physical point of view. To discuss it adequately in 

 its medical aspect would require much more space 

 than is here possible. Details of the very great 

 number of surgical and other cases that have been 

 treated within the last three years would well fill a 

 good-sized volume. The subject has, in fact, been 

 very ably treated by Dr. Walsh in his " Rontgen 

 Rays in Medical Work," which book should form 

 part of a radiographer's outfit. In addition to this, 

 the " Archives of the Rontgen Ray," published by 

 the Rebman Company, is a valuable journal, as it 

 keeps the worker quite up to date in the subject ; 

 the reports and proceedings of the Rontgen Society 

 of London being included in its pages. 



Two of the chief aims of X-Ray experimenters 

 have been the obtaining better definition of the object 

 under examination, whether upon the photographic 

 plate or the fluorescent screen, and being able to 

 localise more accurately the position of any foreign 

 growth or body in the system. Better definition and 

 better contrast will certainly assist the physician in 

 detecting tumours, cancers, and similar soft growths, 



which at present offer so much difficulty owing to 

 there being very little difference in density between 

 them and the surrounding tissues. More accurate 

 localisation will enable the surgeon to perform a 

 quicker and less painful operation in removing any 

 foreign object, or in treating fractures, etc. 



An interesting case of the localising by the aid of 

 radiography, and the consequent removal of a foreign 

 body, is that of a boy three and a half years of age 

 who had swallowed a halfpenny, which had lodged 

 in the oesophagus. He had previously been under 

 treatment for five weeks, during which time he 

 showed no symptoms beyond occasional sickness. 

 A radiograph was taken, which at once revealed the 

 presence of the coin, lodged in the gullet at the level 

 of the second dorsal vertebra. It was ultimately 

 removed by means of a catch carried within a gum 

 elastic catheter. 



Numerous similar examples might be mentioned, 

 all pointing to the great advantage of X-Ray ob- 

 servations, especially in doubtful cases. It is not 

 however in the thorax only that foreign bodies have 

 been localised— the abdomen has been the receptacle 

 for coins and other articles. Foreign bodies have 



