14 ROYAL SOCIETY OF CANADA 



Within a few days of the arrival of the news of Dr. Eoentgen's dis- 

 covery. Professor Cox of McGill Univerdity was able to photograph the 

 l)ones of the hand, with one of the Crookes tubes belonging to the Physics 

 Building. On Februarj' 7th, he succeeded in making the tirst applications 

 of this process to surgery, on this continent, bj" photographing the loca- 

 tion of a bullet in the leg of a patient. An account of the experiments 

 and of the extraction of the bullet, is given in the Montreal Medical 

 Journal, March, 1896. 



Since that date, he has been engaged, in conjunction with Professor 

 Callendar, in investigating the conditions of the production of the Roent- 

 gen rays, and the l)cst method of ol^taining clear and quick photogi'aphs. 



The McDonald Physics Building was fortunately well eqiiipped with 

 mercury pumps, and with all the apparatus necessary for making and 

 exhausting high vacuum tubes. When it was found that of the tlfty 

 Crookes tubes in the laboratory only two were suflftciently exhausted to 

 take photographs, and that somewhat feeblj', the mercury pumps were 

 set in action as soon as the rare intervals of lecture work would permit, new 

 tubes were made and old tubes re exhausted to satisfy the urgent appeals 

 of the medical profession. Several successful photographs were taken, 

 showing the location of bullets and needles, and the nature of fractures. 

 Concurrently with these practical applications, experiments were made 

 to verify the properties and nature of the kathode rays as determined by 

 Lenard and Roentgen, and to find the best form of tube to use, and the 

 best condition.s for taking kathode photogra])hs and for seeing through 

 the body with the tluoroscope. 



Of all the Crookes tubes, that known as the " Focus " tube proved to 

 be In' far the best in point of quickness, clearness and penetration. 

 In this tube, the kathode raj'S are brought to a sharp focus on a plate of 

 platinum ; the rays ]>roeeeding from this focus-point in sti'aight lines are 

 of great intensity and cast very sharp shadows, in the form of tube 

 commonh' advertised and sold in this country, the rays are projected on 

 to the glass wall of the tube, and the focus cannot be made sharj) or much 

 power employed loi- fear of melting the glass. This is the reason why 

 Edison, Tesla, and others in the States have achieved such poor results 

 as compared with those obtained in Europe, where the focus tube has 

 been largely used. Some of the results obtained with a focus tube made 

 and exhausted in the McDonald Physics Building will be exhibited in 

 Section 111. They include ]jhotographs of the skull and of the thickest 

 parts of the body taken with exposures of one quarter to half an hour. 

 Some of these show clearly buttons, hooks, etc., which were separated 

 from the photographic plate by a thickness of six or eight inches of 

 solid flesh and bone. 



In a vacuum, the kathode rays are subject to magnetic infliience, but 

 Lenard has shown that, once in the air, they are unaffected by it. The 



