238 



NA TURE 



[July 5, 1906 



resources amongst various organisations which are in some 

 respects rivals. Principal Riicker had recently said that 

 " any organisation to be visible must be on a grand scale." 

 It is only by combination that the colleges of London can 

 hope to attract the support which is so urgently needed. 



SOCIETIES AND ACADEMIES. 

 London. 



Koyal Society, March 8. — "The Microfcoi ic Chang' s in 

 the Nervous .System in a Case of Chronic Dourine or Mai 

 de Coit, and Comparison of the Same with Those found 

 in .Sleeping Sickness." By Dr. F. W. Mott, F.R.S. 

 (From the Pathological Laboratory of the London County 

 Asylums.) 



The author describes the changes in the central nervous 

 system of an Arab stallion, which acquired the disease by 

 infective coitus. After exhibiting 156 characteristic 

 cutaneous plaques, together with marked symptoms of 

 paraplegia, it died 27^ months after infection. The 

 material was forwarded by Dr. Lingard, director of the 

 Imperial Bacteriological Laboratory of India, who has 

 written an interesting monograph on dourine. A full de- 

 scription of the etiology and clinical symptoms of this 

 disease is contained in this monograph, and an account 

 in detail of this particular case. 



Dourine is due to a specific form of trypanosome, affects 

 pquines, and is transmitted, like syphilis, by coitus. This 

 is of especial interest, since the Spirochaeta pallida has 

 been shown to be the infecting agent in syphilis. 



.\ comparative examination of the tissues of the central 

 nervous system in this disease and in sleeping sickness, 

 experimental and human, appears to show that prolonged 

 trypanosome infection results in a chronic lymphadenitis, 

 followed later by a chronic interstitial inflammation of the 

 lymphatic structures of the nervous system. The morbid 

 process in the case of dourine starts in one seat of primary 

 infection, extends to the inguinal glands, and thence (pre- 

 sumably by the pelvic lymphatics) spreads by the lumbo- 

 sacral nerves to the posterior spinal ganglia, where it mav 

 set up an intense inflammatory process with destructive 

 atrophy of the cells. This destruction of the trophic 

 sensory centres which was found in this case of dourine 

 would account for the cutaneous eruption which occurred 

 during life. It would account also for the marked de- 

 generation of the posterior roots and the sclerosis in the 

 posterior columns, especially in the root zones. The lesion 

 in some respects therefore resembled locomotor ataxy, and 

 it is of interest to note that cases of dourine have occurred 

 in which fractures and dislocations have been observed 

 — due probably to neurotrophic changes. Moreover, there 

 were other signs of chronic irritation observed elsewhere 

 in the spinal cord and nervous system, viz. subpial and 

 septal proliferation of the glia tissue. Marck has described 

 the disease as an infective polyneuritis ; there were reasons, 

 however, in this case, for supposing that the motor nerves 

 were not affected by a degenerative change in the same 

 way as the posterior roots. 



March 22. — " A Note on the Theory of Directive 

 Antennae or Linsymmetrical Hertzian Oscillators." By 

 Prof. J. A. Fleming, F.R.S. 



This paper deals with the theory of bent or unsvm- 

 metrical Hertzian oscillators, .\s is well known, a 

 straight linear oscillator radiates equally in all directions 

 around the axis. It has been found, however, bv Mr. 

 Marconi that if an antenna for electric-wave telegraphy 

 is bent so that a short part of its length, rising from the 

 earth, is vertical, and the greater part horizontal, and 

 therefore parallel to the earth, such an oscillator radiates 

 less in the direction in which the free end points than in 

 the opposite direction.' This is of great practical import- 

 ance, and the writer accordingly investigated mathe- 

 matically the behaviour of a simple case of an unsvm- 



1 .See Proc. Roy. .Roc, vol. Ixxvii. p. J4t,, igo6. O Marc-mi, "On 

 Methods whereby the Radiation of Electric Waves may be mainly contiiT'd 

 to certain Direction^, and whereby the Receptivity of a Receiver may he 

 restricted to Electric Waves emanating from certain Directions." 



NO. 1914, VOL. 74] 



metrical oscillator consisting of three siiriple oscillators 

 of equal electric moment ^ superimposed so as to inake 

 a doubly bent oscillator of the shape Q. 



If V denotes the scalar potential at a point in the field 

 at a distance r large compared with the dimensions of 

 the oscillator, and F, G, and H the components of vector 

 potential, then it is shown in the paper that 



t/n 



+ h 



F = o, = * "5:, H 



rf-n 



i dydz 



dz. 



ayat 



wher.' n= sin (mr — «()/»■, and from these expressions the 

 electric (E) and magnetic (H) force at various points in 

 the field can be obtained. The final result is to give ex- 

 pressions for these forces normal to the radius vector 

 drawn in the equatorial plane of symmetry as follows : — 



H 



ipvmr 



M 



-•M' 



.j,,[(„,„=,=-,iti^'^7 



(<pi. 



-+l cos 



1"]' 



•)■']' 



where cos is the azimuthal angle the radius vector makes 

 with the axis of the oscillator reckoned from the direc- 

 tion in which the free ends point. These expressions show 

 that as increases from 0° to 180° the values of E and 

 H vary, and are greater when 6*= 180° than when ^ = 0°. 



Hence there is an unsymmetrical radiation by such an 

 oscillator, greatest in the direction opposite to that in 

 which the free ends point. 



Such an oscillator may also be regarded as the combin- 

 ation of a completely closed conductive circuit or mtiguctic 

 oscillator with a straight or open electric oscillator. The 

 field of the magnetic oscillator was investigated by the 

 late Prof. G. F. Fitzgerald (see his scientific writings, 

 edited by Prof. J. Larmor, Sec.R.S., p. 128) prior to the 

 date of Hertz's discoveries, and in the discussion at the 

 Royal Society on March 22 on Mr. Marconi's paper, 

 loc. cit., it was pointed out by Prof. J. Larmor that a 

 bent oscillator of the kind above discussed was equivalent 

 in electromagnetic action to a magnetic plus an electric 

 oscillator. 



May 3. — " On a Static .Method of Comparing the Densi- 

 ties of Gases." By R. Threlfall, F.R.S. 



Since it is a simple matter to make a manometer show- 

 ing differences of gas pressure of a few centimetres of 

 water, accurate to between i/ioo mm. and i/iooo mm., 

 according to the construction, it is possible to determine 

 the relative densities of gases by a method siinilar to the 

 one employed by Regnault in determining the temperature- 

 density variation of mercury. 



It is shown that, using gas columns 20 metres long, the 

 difference of density of " chemical " and " atmospheric " 

 nitrogen should be capable of observation. The author 

 has employed the method in a comparison of the densities 

 of producer gas and air, using gas columns about 

 20 metres in height. The two columns of gas and air re- 

 spectiveh- were contained in composition pipes twisted 

 together and iinmersed in water in an outer iron pipe 

 through which a stream of water passed. 



In two experiments on two different samples of gas 

 differences of pressure of 0-3458 cin. and 03550 cm. of 

 water respectively were observed, and producer-gas densi- 

 ties accurate to about i, '5000th part in terms of the density 

 of air were deduced. The commercial micromanometer 

 made by the Cainbridge Scientific Instrument Co. to the 

 author's designs was employed in these comparisons, and, 

 since it is possible to construct an instrument say five 

 times as sensitive, and to use columns of gas at least 

 twice as long without inconvenience, the method should 

 yield values of relative density correct to i part in 10,000 

 without difiicultv. 



