574 



NATURE 



[April \2, 1888 



the stoneware and inner porous vessels usually employed 

 for Grove's cells, the porous vessel being cemented into the 

 outer stoneware vessel (by paraffin wax or other unattacked 

 material) in such a fashion as to divide it into three compart- 

 ments separated one from the other by porous dividing walls ; the 

 acid and alkaline fluids being placed in the two outermost com- 

 partments, and the innermost one being filled with a solution of 

 ajneutral salt, e.g. sodium sulphate. 



March I. — "On Electdcal Excitation of the Occipital Lobe 

 and adjacent Parts of the Monkey's Brain." By E. A. 

 Schafer, F. R. S. , Jodrell Professor of Physiology in University 

 College, London. 



The following are the results of my own observations: — 

 Electrical excitation of the posterior limb of the angular gyrus, 

 of the upper end of the middle temporal gyrus ^ (which is con- 

 tinuous with it), of the whole cortex of the occipital lobe, inclusive 

 of its mesial and under aspects and of the quadrate lobule, 

 causes conjugate deviation of the eyes to the opposite side. The 

 movement is not, however, in all cases a simple lateral deviation, 

 but the lateral movement may be combined with an upward or 

 downward inclination according to the part stimulated. Thus — 



(i) Excitation of a superior zone which comprises on the exter- 

 nal surface the posterior limb of the angular gyrus, the upper 

 (posterior) end of the middle temporal gyrus, and the part of the 

 occipital lobe immediately behind the external parieto-occipital 

 fissure and on the mesial surface the quadrate lobule immediately 

 in front of the upper end of the internal parieto-occipital fissure 

 and the occipital lobe for a short distance behind the upper end 

 of that fissure, produces, besides the lateral deviation, a down- 

 ward inclination of the visual axes which is sometimes— especially 

 when the stimulation is applied at or near the mesial surface — 

 so marked as greatly to obscure the lateral deviation. 



(2) Excitation of an inferior zone comprising the whole of the 

 inferior surface of the lobe, the lower part of the mesial surface, 

 and the posterior or lowermost part of the convex or external 

 surface, produces, besides the lateral deviation, an upward 

 inclination of the visual axes, which, like the downward move- 

 ment resulting from stimulation of the superior zone, may be so 

 marked as partly to obscure the lateral deviation. 



(3) Excitation of an intermediate zone which comprises the 

 greater part of the external surface (where it gradually broadens 

 out laterally) and extends over the margin of the great longitu- 

 dinal fissure to include a narrow portion of the mesial surface, 

 produces neither upward nor downward inclination of the visual 

 axes, but a simple lateral movement. 



If, as is highly probable, the movements of the eyes, which 

 occur on excitation of the occipital lobe and adjacent parts, are 

 the result of the production of subjective visual sensations, these 

 effects of excitation of the several parts of that lobe and the 

 adjoining portions of the brain would appear to indicate — 

 * I. Aconnectionof the whole visual area of each hemisphere with 

 the corresponding lateral half of each retina. (This has already 

 been ascertained to be the case from the result of removing the 

 whole of the area on one side, bilateral homonymous hemianopsia 

 being thereby produced. ) 



(2) A connection of the superior zone with the superior part of 

 the corresponding lateral half of each retina. 



(3) A connection of the inferior zone with the inferior part of 

 the corresponding lateral half of each retina. 



(4) A connection of the intermediate zone with the middle 

 part of the corresponding lateral half of each retina. 



" A Comparison of the Latency Periods of the Ocular Muscles 

 on Excitation of the Frontal and Occipito-Temporal Regions of 

 the Brain." By E. A. Schafer, F.R.S., Jodrell Professor of 

 Physiology in University College, London. 



Conjugate deviation of the eyes to the opposite side is pro- 

 duced by excitation of entirely different regions of the cerebral 

 cortex. 



Of these parts, excitation of which produces this result (con- 

 jugate deviation of the eyes to the opposite side), one, viz. the 

 frontal area, is distinguished from the rest by the fact that its 

 removal produces paralysis of that movement. This fact has 

 been seized upon by Ferrier as indicating an important functional 

 difference, the movements in the one case being probably caused 



Excitation of the upper end of the superior temporal gyrus gives a 

 similar result. Since this is commonly accompanied by a movement of the 

 opposite ear, it is usually considered that subjective auditory sensations have 

 been called up by the excitation. 



by the direct action of this part of the cortex upon the centre of 

 origin of the nerves to the ocular muscles ; but in all other cases 

 by indirect action, the movement when, e.g., the visual or 

 auditory region is stimulated being the result of visual or 

 auditory impressions (subjective sensations) being provoked in 

 the brain by the excitation, and these impressions producing 

 indirectly the action in question. Others have supported the 

 view that in all cases the movement is the result of the setting 

 up of subjective sensations, but that in the case of the frontal 

 area these are tactile or are connected with the muscular sense. 



It seemed to me that light would be thrown upon the question 

 if the period of latent stimulation of the ocular muscles were 

 accurately determined under exactly the same conditions for the 

 frontal and posterior (temporal and occipital) areas respectively. 

 The result of this determination, which I have made in a number 

 of monkeys, is to show that the latent period is longer by some 

 hundredths of a second in the case of stimulation of the occipital 

 lobe, or of the superior temporal gyrus than when the frontal 

 area is stimulated ; thus indicating that in the former case the 

 nervous impulses must be transmitted through at least one more 

 nerve centre than in the latter. 



Geological Society, March 28.— Dr. W. T. Blanford, 

 F. R. S., President, in the chair. — The following communications 

 were read : — On some eroded agate pebbles from the Soudan, 

 by Prof V. Ball, F. R. S. The majority of the pebbles in a 

 collection made by Surgeon-Major Greene in the Soudan, and 

 presented by him to the Science and Art Museum in Dublin, are 

 of vei-y similar character to the agate and jasper pebbles derived 

 from the basalts of India. It may be concluded inferentially 

 that they came originally from a region in which basaltic rocks 

 occur to a considerable extent. A certain number of them are 

 eroded in a manner unlike anything noticed in India, though it 

 is probable that similar eroded pebbles will eventually be found 

 there. Throughout India, wherever there is a deficient subsoil- 

 drainage or excessive evaporation and limited rainfall, salts are 

 apparent either in supersaturated subsoil-solutions or as crystal- 

 lizations in the soil. They are most abundant in basaltic regions, 

 and in a lake occupying a hollow in the basalt in Berar carbonate 

 of soda is deposited in abundance from the water, which becomes 

 supersaturated during the summer. The author commented on 

 the efficacy of such a liquid as a solvent of silica, and noticed 

 the selective action of the agent which had affected the Soudan 

 pebbles and had corroded some layers more than others ; he 

 suggested that, while this might be to some extent due to differ- 

 ences in composition, it was more probably owing to differences 

 of nodular constitution. He considered it unnecessary to refer 

 to the action of humic acid, because, while the salt to which 

 the solvent action is attributed would be capable of doing such 

 work, and would be probably abundant in the region referred 

 to, we could not expect any great amount of humic acid in the 

 same area. This paper gave rise to a discussion, in the course 

 of which remarks were made by the President, Mr. Whitaker, 

 Mr. Irving, Mr. De Ranee, and Sir Warington Smith. — On the 

 probable mode of transport of the fragments of granite and 

 other rocks which arefound embedded in the Carboniferous Lime- 

 stone of the neighbourhood of Dublin, by Prof. V. Ball, F.R.S. 

 — The Upper Eocene, comprising the Barton and Upper Bag- 

 shot formations, by J. Starkie Gardner and Henry Keeping, 

 with an appendix by H. W, Monckton. 



Royal Microscopical Society, March 14. — Dr. R. Braith- 

 waite, Vice-President, in the chair. — The Rev. A. H. Cooke 

 exhibited a number of photomicrographs of the odontophores of 

 Mollusca, as an attempt to illustrate this group of objects by 

 photography ; he also referred to the valuable results obtained in 

 the definition of species by the application of the method. — Mr. 

 E. M. Nelson exhibited and described a new form of mechanical 

 stage, in which two points were moved by milled heads in rect- 

 angular directions, carrying the slide with them, the slide being 

 pressed against them, when they were withdrawn, by the hand. — 

 Mr. C. L. Curties exhibited a new combination condenser, which, 

 in addition to the condenser, also contained an iris diaphragm, 

 a spot lens, and a polarizing prism. — Mr. [Crisp exhibited a 

 Collins's aquarium microscope which could be fixed by suction to 

 the glass side of the tank ; also Klonne and Miiller's aquarium 

 microscope for examining objects in a small aquarium or trough 

 specially constructed for the purpose, and fitted with movable 

 diaphragm slides ; also a new form of Thury's 5-tube micro- 

 scope for class purposes, having a reflecting prism made to 

 rotate, so as to exhibit the object upon the stage alternately to 



