March 5, 1896] 



NATURE 



425 



First, I have the honour of laying before the Academy some 

 photographs taken by the well-known method indicated by 

 Rontgen ; for, besides being excellent photographs, they show 

 some new features. The photographs are : — 



(1) Those of various metals (magnesium, aluminium, iron, 

 lead, zinc, copper, palladium, silver, gold, and platinum) 

 photographed together on the same plate. They confirm the 

 relation found by Rontgen between the transparency and 

 'lensity. 



(2) Photographs of the same metals, and further a scale of 

 xiisparency, obtained by photographing the shadow of a thin 



icctangular slab of aluminium having one side tapered. These 

 photographs are those I took in seeking for a possible colour- 

 effect, placing between the Crookes' tube and the metal sheets 

 various substances, such as cardboard, aluminium, sheets of gold 

 and silver, &c. In spite of these being interposed, the photo- 

 graphs, when compared with the scale of transparency, show the 

 same relative intensity. 



(3) A photograph of the shadow of my hand. This kind of 

 picture shows, as is well known, the bones, and not only the 

 phalanges of the fingers but also the whole metacarpus is seen. 

 It is noticeable that the cartilages are far less transparent than 

 they appear in the pictures published in the journals, and, on the 

 contrary, the spongy' parts of the phalanges are more transparent. 



(4) A photograph of the shadow of the oedematous hand of a 

 corpse (that of a woman aged fifty-nine) ; in the second phalange 

 of the index-finger was fixed an iron nail ; that of the middle 

 finger was broken by a hammer ; in that of the third was intro- 

 duced a small drop of mercury ; finally, the palm of the hand 

 was pierced with a needle, which was entirely hidden in the 

 flesh. In the photograph these details are all clearly shown. 

 Besides all the phalanges of the fingers and the metacarpus, 

 which are clearly visible with all the joints, the carpus can just 

 lie distinguished. Here also may be noticed that the cartilages 

 are not very transparent, and the spongy parts of the phalanges 

 sho-zu tip well. 



( 5 ) A photograph of the same hand ; besides the phalanges of 

 'le fingers and metacarpus may be seen clearly defined the small 



n,:s of the carpus with their details, and further the portion 

 lotographed of the radius and the cubitus. The peculiarities 



-hown by the cartilages and spongy parts are repeated also in 



this example. 



(6) Two photographs of an artifically paralysed frog, taken with 

 ry differe)it exposures. I would call attention to one point, 

 not hitherto noticed, as far as I know — which may interest 



lis Academy of Medicine ; in one of these photographs may be 

 seen, besides the bone structure, the two lungs ; in the other, 

 hesides the lungs, the heart, and another internal organ, which I 

 conclude is the spleen. As might be expected, the lungs appear 

 the more transparent. 



I shall now relate the observations I have made by eye. 

 First I propose to consider the reason that the human eye is 

 not directly sensitive to the Rontgen rays. A priori there is no 

 impossibility in these rays exciting a luminous sensation. The 



henomenon of persistence of vision with ordinary light may be 

 ! ributed to a fluorescence of the retina or optical system of the 



ic. Now, Rontgen has found that to a certain extent bodies 

 iluorescent to ordinary light are so also to his rays. Were this 

 the case with the retina, it is obvious that the rays could give a 

 luminous sensation, since they would produce actual light on the 

 retina. With this idea I made some experiments on a retina 

 taken from the eye of a living rabbit. Observations made with 

 this living retina showed that, while somewhat fluorescent to 

 the direct light issuing from a Crookes' tube, it gave no indica- 

 tion of fluorescence with the Rontgen rays. I should mention, 

 however, that my two observations are not sufficient absolutely 

 to exclude such a property from the living retina, as the pheno- 

 mena shown by the Crookes' tube, with which I have hitherto 

 worked, are not very intense. 



I next examined photographically the transparency to Rontgen 

 rays of the crystalline lens of the eye, and I obtained the result 

 that the lens, together with the various media forming the optical 

 .system of the eye, intercept the rays to approximately the same 

 extent a sa sheet of glass one millimetre thick ; that is to say, 

 they are only slightly transparent. Trials of the separate portions 

 of the eye showed that the crystalline lens was the most opaque 

 part, while the cornea was the most transparent. The conclusion 

 I derive from these results is that, though the retina may be 

 fluorescent to the Rontgen rays, as is the glass of the photo- 

 graphic plate, it is hardly probable that it could see objects 



NO. 1375, VOL. 53] 



directly through layers of wood, aluminium, flesh, &c. This, 

 however, does not exclude the possibility of seeing them in- 

 directly, by transforming, so to say, the Rontgen rays 

 into ordinary luminous rays before they reach the eye. 

 I have made a simple arrangement by means of which I can 

 distinctly see the shapes of bodies enclosed in boxes of card- 

 board, aluminium, cVc. This cryptoscope, which I have the 

 honour of showing to the Academy, consists of a small cardboard 

 tube about 8 centimetres high. One end is closed by a sheet of 

 black paper, on which is spread a layer of fish-glue and calcium 

 sulphide (there being no barium and platinum cyanide at hand); 

 this substance I have found to be very phosphorescent under the 

 action of Rontgen rays. Within the cardboard tube, at the 

 other end, at which the eye is placed, is fixed a lens, giving a 

 clear image of the phosphorescent paper. On looking through 

 this cryptoscope one can see, even in a light room, the shape and 

 position of metallic bodies enclosed in boxes of cardboard, wood, 

 aluminium, and within the flesh. Its action is obvious ; the fluores- 

 cent paper under the action of the rays is illuminated only in those 

 portions which receive rays, consequently the silhouettes of the 

 objects intercepting the rays appear dark. In this there is, ot 

 course, nothing new which could not have been deduced from 

 the original experiments of Rontgen ; the novelty, if indeed it 

 is so, consists merely in making use of the known facts to 

 design the arrangement. It seems to me that, in a more per- 

 fected form, it might be of extensive use in surgical and medical 

 science. The sulphide of calcium may be replaced with advan- 

 tage by the cyanide of barium and platinum. It is further clear 

 that when, by a camera or other means, not only the shadows, 

 but also the images, can be photographed (which, I believe, 

 Profs. Battelli and Garbasso, of Pisa, have already succeeded in 

 doing) the same cryptoscope will render visible also the images 

 of bodies enclosed in boxes of wood or other materials. 



As soon as possible I shall communicate the results of experi- 

 ments I have begun with the view of shortening the necessary 

 exposure by means of sensitive plates containing phosphores- 

 cent substances, or sensitive films backed by phosphorescent 

 papers. 



Finally, I wish to off"er my warmest thanks to my honoured 

 colleague G. Pisenti, Professor of Pathology, and Rector of the 

 University, who has given me every possible assistance, and 

 himself prepared the various portions of the eye with which I 

 made the experiments. 



THE LONDON CITY COMPANIES' GRANTS 

 TO SCIENCE AND EDUCATION. 



T T is well known that some of the London City Livery Com- 

 -*■ panies make liberal grants for the jiurposes of education and 

 research. In order to elicit information as to the extent and 

 amount of such grants, we communicated a few months ago with 

 the chief London Companies, and succeeded in obtaining several 

 valuable statements. A few of the Companies sent us complete 

 accounts of what they have done and are doing for the promo- 

 lion of education and scientific investigation, but others only gave 

 information concerning some of the grants made. The facts 

 which follow do not, therefore, represent a complete statement 

 of the assistance rendered by the Livery Companies, but they will 

 serve to show the extent of the gifts. The Companies are 

 mentioned in the order of civic precedence. 



The Grocers' Company, in addition to making large annual 

 grants for general educational purposes, established in 1883, and 

 still maintain, three scholarships of the value of ;i^250 a year for 

 the encouragement of original research in sanitary science. 

 Among the names of those who have held these scholarships 

 are Dr. Wooldridge, Dr. Woodhead, and Dr. MacFadyen. 

 Further, in 1894, the Company gave the sum of ;i^lo,CKX) to the 

 British Institute of Preventive Medicine. 



It is almost impossible to give an adequate idea of the educa- 

 tional work done by the Drapers' Company. For several years 

 the Company have been deeply impressed with the importance 

 of encouraging education, and especially of assisting clever 

 children among the poorer classes to obtain higher education. 

 With this view they established in the year 1875, and have 

 annually given since that date, five scholarships, each of the 

 value of ^30 per annum, and tenable for four years at places of 

 education higher than elementary. These scholarships are 

 offered for competition by boys and girls attending metropolitan 

 public elementary schools. In the year 1889, the Company 



