;54 



NA TURE 



[February 8, 1894 



anterior commissure, the tract is continued backwards on either 

 side of the infundibulum into the red nucleus below and ex- 

 ternal to the aqueduct at the plane of exit of the third nerve. 



B. Increased Action. 



II. Acceleration. — Commencing from a point on the convex 

 surface of the cortex within the "sensori-motor " area, the effect 

 may be followed back just below the lenticular nucleus where it 

 borders on the outer and ventral portion of the internal capsule ; 

 the strand runs at first external and then ventral to the motor 

 portion of the internal capsule, and so reaches the tegmentum. 

 The lines from the two sides meet in the interpeduncular grey 

 matter at the level of and just behind the exit of the third 

 nerve. 



III. Hyperinspiratory Clonus ("snuffing movements"). — 

 This eftect was obtained by excitation at the junction of the 

 olfactory bulb and tract, and then carrying the stimulation 

 backwards along the olfactory tract; the same result was found 

 when the uncinate convolution of the temporo-sphenoidal lobe 

 was irritated. P'oUowed from the uncus this excitable region 

 passed behind the optic tract to the crus, and then lay ventrally 

 to the crusta. The excitable tract on each side thus converged 

 towards the middle line at the upper border of the pons. 



JV. Hyperinspiratory Tonus. — This experimental result is of 

 such frequency and constancy as to be clearly an important 

 general phenomenon. It can be elicited in various ways : e.g. 

 excitation of the descending motor tract in the corona radiata 

 and internal capsule yielded this result ; so did excitation of the 

 fifth nerve and dura mater, as well as the sciatic nerve, both be- 

 lore and after complete removal of the cerebrum at the 

 tentorium cerebelli. 



"Experimental Researches into the Functions of the 

 Cerebellum." By Dr. J. S. Risien Russell, Assistant Physician 

 to the Metropolitan Hospital. 



This paper is based on experiments performed on dogs and 

 m.onkeys, the results of which lead the author to conclude that 

 the cerebellum is an organ whose one lateral half does not in 

 any great measure depend on the cooperation of the other half 

 for the proper performance of its functions. The bulk of the 

 impulses pass from one half of the organ to the cerebrum, or 

 spinal cord, without pa-sing to the other half. Three factors 

 are responsible for the defective movements which result on 

 ablation of different parts of the organ- — incoordination, 

 rigidity, and motor paresis. The last of these is probably 

 directly due to the withdrawal of the cerebellar influence from 

 the muscles, while the exalted excitability of the opposite 

 cortex cerebri, which resulis after unilateral ablation of the 

 cerebellum, is probably a provision for compensation in this 

 and other connections. The alteraiion in the excitability of the 

 cerebral cortex was the most striking result obtained, for both 

 as tested by the induced current directly applied to the cortex, 

 and from the characters of the curves obtained from muscles on 

 Ihe two sides of the body, during general convulsions evoked 

 by absinthe, the opposite cortex showed a greater degree of 

 excitability than did that on the same side, owing, it appears, to 

 an increased state of excitability of the cortical cells of the 

 opposite cerebral hemisphere, and a diminished state of excit- 

 ability of those on the same side. Further, the curves obtained 

 from limb muscles showed that there was a marked alteration 

 in the second stage of the convulsive seizure, on the side of a 

 unilateral ablation of the cerebellum, or on both sides after 

 total ablaiion of the organ, for the tonus characteristic of this 

 stage of similar convulsions evoked in dogs whose central 

 nervous S)siem was intact was eiiherreplaced by clonic spasms, 

 or a large element of clonus was superimposed on the tonus. 



There is evidence that the one half of the cerebellum con- 

 trols the cells of the cortex of the opposite cerebral hemisphere, 

 and those ol the anterior horns of the spinal cord on the same 

 side chieflv, and on the opposite side to a slight extent. It is 

 further suggested that either the cerebral hemisphere whose ex- 

 citability is increased inliiliits the opposite hemisphere, or that, 

 under norm.il conditions, one half of the cerebellum inhibits 

 the other half, which inhibition being no longer operative, 

 owing to ablation of half ol the organ, allows the remaining 

 half to exett an increased control on the opposite cortex cerebri, 

 or on the spinal centies of the same side, or possibly in both 

 directions ; but which is the mo^t probable explanation of the 

 phenomena idiserved is at present left an open question. 



The syni, toms which characterise ablation of different parts 

 of the cerebellum are detailed ; and it is urged that instead of 



Nt>. ' 267, VOL. 49] 



looking on it as a distinct organ which has a special function, 

 distinct from those subserved by other parts of the central 

 nervous system, it would be more correct to look on it as a part 

 of that system, having many functions in common with other 

 parts of it, the chief difference between one part of this great 

 system and another being the degree in which different func- 

 tions are represented in any given part : e.g. with regard to 

 motor power, the anterior extremity is maximally repre- 

 sented in the cerebrum and minimally in the cerebellum, 

 whereas the trunk muscles are minimally represented in the 

 cerebrum and maximally in the cerebellum. Arguments are 

 adduced in favour of looking on the ocular deviations which 

 result from ablation of parts of the cerebellum as paralytic 

 rather than irritative phenomena, and two forms of nystagmus 

 are recognised as consequent on cerebellar lesions, one which is 

 spontaneous, and the other which is only evoked on voluntary 

 movements of the globes, and the probable difference in their 

 aetiology discussed. Finally, the phenomena characteristic of 

 unilateral ablation of the cerebellum are contrasted with those 

 the result of extirpation of the labyrinth, and it is shown that 

 no single phenomenon is the same in the two. 



" The Pathology of the Gidema which accompanies Passive 

 Congestion." By Walter S. Lazarus-Barlow. 



Physical Society, January 26. — Prof. A. W. Riicker, 

 F.R.S., President, in the chair. — Mr. J. W. Kearton read a 

 note on a new mode of making magic mirrors. The author's 

 first idea was that the magic properties were due to differences 

 in reflecting power, but experiments showed this to be im- 

 probable, and indicated that the patterns visible by reflected 

 light were due to slight concavities in the surfaces. Several 

 methods of producing such changes of curvature were tried, such 

 as electro-depositing and electrical etching, the plates being sub- 

 sequently polished to remove sharp edges. The method found 

 most satisfactory was to draw the figures on polished brass 

 covered with wax, and etch them by immersing in nitric acid, 

 subsequently scouring with charcoal, Sheffield lime, and swans- 

 down calico, until all direct traces of the figures disappeared. 

 The scouring rounds off the edges and makes the depressions 

 concave, the two eventually forming one concave sweep, which 

 makes itself visible when light is reflected from it on a screen. 

 To obtain satisfactory results with figures having broad and 

 narrow lines, it was found necessary to paint over with hot wax 

 the fine lines, and the outer edges of the broad ones after the 

 first immersion ; a second immersion etched the middle parts 

 of the broad lines deeper. By repeating the process the broad 

 lines were etched roughly concave in steps, and the scouring 

 made their curvature continuous. Figures in relief, show- 

 ing the paitern in shade on reflection, were obtained by 

 painting the pattern on the plate in sealing-wax dissolved in 

 naphtha, and etching away the uncovered portions by an immer- 

 sion of one or two seconds. A number of mirrors with patterns 

 in intaglio and relief were exhibited to the meeting. Prof 

 S. P. Thompson said the chief interest of Mr. Kearton's work 

 was that he had succeeded in producing mirrors by a process 

 which Prof. Ayrton had found unsuccessful. The spherical 

 polisher used by Mr. Kearton might have something to do with 

 the result obtained. Some of the mirrors had been gilt after 

 polishing, and the reflected pattern improved thereby. Prof. 

 Ayrton said he was greatly interested to see that mirrors could 

 be produced by the chemical method. The polisher used by 

 the Japanese was the flat end of a tight bundle of special straw 

 cut crosswise. When the true explanation of the magic proper- 

 ties was found out, the chemical method was nut pursued 

 further. The Rev. F. J. Smith mentioned that he had pro- 

 duced magic properties on silvered glass by the inductoscript 

 method. Although no markings could be seen directly, the 

 paitern showed itself when light was reflected from the surface 

 to a screen. — Mr. W. B. Crolt read a paper on some obser- 

 vations in diffraction, and exhibited a large number of photo- 

 graphs of diffraction figuies obtained under different conditions. 

 Ihe first series exhibited, related to diffraction Irom parallel 

 light (diffraction of Fraunholerand Schwerd), and were obtained 

 liy placing various combinaiitms of thin circular lines of 

 light on a dark glass plate before the object-glass of a telescope i 

 focussed on a star. Spectral images ol the star are formed by i 

 interference from the eilges of the lines, thus giving diffraction ! 

 patterns whose form depends on the shape of the aperture em- 

 ployed. The next series illustrated diftraction in shadow 

 (Fresnel's diffraction), and were produced by condensing 



