June 17, 1897] 



NATURE 



i6i 



The following are among recent appointments : — Dr. J. 

 Franz, Assistant Professor of Astronomy at Konigsberg, to be 

 Director of the Breslau Observatory, and Professor of Astronomy 

 in the University there ; Dr. Freeh to be full Professor of 

 (ieology in the University of Breslau ; Dr. Carl Paal to be full 

 Professor of Pharmaceutical and Applied Chemistry in the 

 University of Erkngen ; Dr. Paul Samassa to be Associate 

 Professor of Zoology in the University of Heidelberg ; Dr. 

 Bredt, of Bonn, to be full Professor of Chemistry in the 

 I'olytechnic Institute at Aix ; Dr. E. B. Copeland to be 

 Assistant Professor of Botany in the University of Indiana ; 

 Mr. William George Hibbins, Whitworth Exhibitioner, and 

 Research Scholar of the Mason College, Birmingham, to be 

 additional Assistant in the Mechanical Engineering Department 

 of the Merchant Venturers' Technical College, Bristol. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, June 3. — " The Sensitiveness of the Retina 

 to Light and Colour." By Captain W. de W. Abney, C.B., 

 D.C.L., F.R.S. Received May 10, 1897. 



The author treats first of the extinction of the sensation of 

 light on the centre of the retina. He made his reduction of the 

 intensity of the light falling on the illuminated spot with a new 

 piece of apparatus, which consisted of a gelatine wedge bent so 

 as to make an annulus. He describes this wedge and its 

 graduation, showing how its readings can be utilised, they 

 being proportional to the logarithm of the intensity of light 

 passing through it. 



It is found that the smaller the spot of illuminated surface, 

 the less reduction in intensity of the light is required, and that 

 the amount of reduction of the light falling on the spot which 

 just produces no sensation of light, is connected with the size of 

 the spot by a simple formula, I = jc»', where I is the intensity 

 and X the diameter of the spot. Further, he finds that it is 

 the smallest diameter which governs the necessary reduction in 

 intensity, and not the area of the illuminated surface. Having 

 experimented with the extinction of light at other parts of the 

 retina, he finds that it obeys the same law. Since a large and a 

 small area having the same actual illumination appear to be of 

 different brightness, an investigation was made of the relative 

 luminosities of the two, and it was found that the two were con- 

 nected by a very simple law. 



The reduction of the intensity of a coloured ray to extinguish 

 all colour was next measured with areas of different dimensions, 

 and it was shown that again the intensity of the reduced light 

 was connected with the size of the spot by a simple expression 

 similar to that of the extinction of all light, but the exponential 

 coefficient differed, indicating that light and colour were not 

 connected together in the manner which might be expected. 



The author then deals with the question of colour fields, and 

 finds that all colour fields are of the same form, the extent 

 depending solely on the illumination and the area of the surface 

 the image of which fails on the retina. He finds that there is 

 a connection between the intensity of the colour and the extent 

 of the field which can be expressed by a formula, as also can 

 the connection between the size of the spot of illuminated surface 

 and the extent of field. He gives the curves of illumination for 

 equal colour fields, and the curves of extent of field for every 

 colour in the prismatic spectrum. Finally he makes an investi- 

 gation into the relative sensitiveness to light of various points in 

 the retina, and shows that there are " iso-lumes," or fields of 

 equal sensitiveness, which appear to be of the same form as the 

 colour fields. 



He points out that there are difficulties in reconciling these 

 results with either the Young or Hering theory of colour 

 vision, and suggests a modification in the accepted theory of 

 light and colour which may explain the connection between the 

 two. 



' ' On the Nature of the Contagium of Rinderpest. " By 

 Alexander Edington, M.B., F.R.S.E., Director Colonial 

 Bacteriological Institute, Cape Colony. 



In the following paper it is proposed to communicate to the 

 Royal Society the results of experiments made in South Africa 

 on the infectivity of the blood of animals affected with rinder- 

 pest. The experiments were all made on cattle kept under 

 conditions in which accidental spontaneous infection could with 

 certainty be excluded. These experiments had been concluded 



NO. 1442, VOL. 56] 



in 1896, before the arrival of Dr. R. Koch in South Africa, and 

 their results had been communicated to him on his arrival. 



(i) The blood of an animal ill with rinderpest, when taken 

 during the febrile stage or previous to death, and injected sub- 

 cutaneously or intravenously into healthy cattle, produces the 

 typical disease — rinderpest, provided the blood is prevented from 

 coagulating. 



(2) The onset of coagulation and actual coagulation of the 

 blood exerts a marked destructive influence on the virulence of 

 such blood, 



(3) The best method of obtaining virulent blood is to draw 

 it aseptically from the jugular vein of an animal ill with 

 rinderpest, and to mix it immediately with a i per cent, solution 

 of citrate of potash, the latter previously well sterilised, in the 

 proportion of 2-3 parts of blood to i part of citrate of potash 

 solution. Such blood, as has been shown, remains fluid. 



(4) This citrate of pota.sh mixture of blood proves virulent irk 

 the first few days, generally not exceeding six days ; after six 

 days' keeping the virulence becomes rapidly weakened, so that 

 after nine days the blood mixture is altogether inert. 



(5) Admixture of glycerine to citrate blood does not cateris 

 paribus interfere with the virulence of such blood. Glycerine 

 added to fresh blood does interfere with the virulence of the 

 latter on account of the coagulation of the blood. 



(6) The nasal mucus of an infected animal when used fresh 

 and rubbed into the nostrils of normal cattle, produced in all ■ 

 instances typical rinderpest. We have never had a single failure 

 in attempting to produce the disease by this means. By keeping 

 the nasal mucus, even for a few hours, its virulence becomes 

 markedly less. 



(7) The condition of marked swelling of the lymphatic glands 

 is one of, if not indeed the most evident pathognomic feature of 

 the disease. The contagium exists as a primary infection in the 

 lymphatic glands. 



(8) A very mild attack of rinderpest, such as is produced by 

 injection of blood of greatly decreased virulence, does not con- 

 vey absolute immunity, this latter being produced in proportion 

 to the severity of the attack through which the animal had passed 

 primarily. An animal seemingly affected may have a relapse of 

 the disease, which may go on to fatal issue or be mild in type, 

 leading to recovery. Animals in the latter case always acquire 

 immunity of a high degree. 



Physical Society, June 11.— Mr. Shelford Bidwell, Presi- 

 dent, in the chair. — A mathematical paper was read by Mr. 

 C. S. Whitehead, on the effect of sea-water on induction tele- 

 graphy. If a secondary circuit containing a telephone is rightly 

 placed with respect to the field of a primary circuit traversed by 

 an alternating current, signals may be transmitted over con- 

 siderable distances. The author investigates the effect of filling 

 the intervening space with sea- water ; and, generally, the effect 

 of a spherical conducting shell on the induction, at a poitit in a 

 dielectric, due to an alternating current in a circular circuit, 

 when the axis of the conductor passes through the centre of the 

 shell. In the mathematical treatment, two cases are considered, 

 (i) To find the normal magnetic induction at any point in the 

 dielectric outside the shell when a circular circuit carrying an 

 alternating current is placed in the dielectric inside a spherical 

 conducting shell. (2) To find the normal magnetic induction 

 at any point on the remote side of an infinite conducting plate, 

 due to a circular circuit parallel to the plate. In both cases the 

 following result is arrived at : 



7,. = ,. -!i"I 



where v^ is the maximum value of the normal magnetic induc- 

 tion at any point outside ; w^ the maximum normal magnetic 

 induction due to the current in the primary, supposing the con- 

 ducting shell or plate absent, at the same point ; t\ the thickness 

 of the shell or plate ; and 



C-^)* 



where /t is the permeability of the conducting shell or plate ; 

 <r its specific resistance, p = 2 it times the frequency. If the 

 frequency is 300, / = 1885. For sea- water, a is taken as 

 2 X id'" C.G.S. units ; and /* = i, The sea-depth at the 

 North Sand Head corresponds to rj = 2000 cms. Hence, in 



this case, — = •21, or 79 per cent, is lost. Similarly, when 

 Wo 



