June 8, 1893] 



NA TURE 



141 



meability for the electric flux. — On the diffraction of light at the 

 straight sharp edge of a screen, by Eugen Maey. This work 

 was undertaken to test whether a certain diffraction phenomenon 

 was explainable by the accepted theory of diffraction. The 

 phenomenon in question, as described by W. Wien, consists in 

 the fact that a finely-ground metallic edge, when illuminated by 

 an intense white light, appears as a bright line from points deep 

 in the geometrical shadow. A careful theoretical and experi- 

 mental study of the phenomenon shows that the theory is 

 competent to explain the fact within certain limits, but that the 

 phenomenon is greatly influenced by small differences of excel- 

 lence in the edges, a circumstance which has an important 

 bearing upon the behaviour of gratings. — Absolute measure- 

 ments on the discharge of electricity from points, by Julius 

 Precht. In general, points may be charged highly before 

 discharge begins. Lightning conductors require about 15,000 

 volts, and the finest points 2500. Ultra-violet illumination 

 favours discharge, whereas dust and flame gases diminish it. 

 A bundle of equal points requires a higher potential than a 

 single one. A point discharging positive electricity wears away, 

 whilst a point negatively electrified does not. — Also papers by 

 O. Wiener, J. von Geitler, M. Levy, A. Kossel, and A. Raps. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, May 4. — "Further Experimental Note 

 m the Correlation of Action of Antagonistic Muscles." By 

 ij. S. Sherrington, M.A., M.D. 



In a previous communication (Proceedings of Royal 

 ■society, February i, 1893) it was stated that physiological 

 jontraction, and even mere mechanical tension, of the flexor 

 muscles of the knee exerts considerable physiological influence 

 apon the activity of the antagonistic group of muscles, the 

 •.xtensors. For instance, the elicitation of the "jerk" from the 

 ixtensors can be rendered difficult for a time by appropriate 

 ';xcitation of the flexors, and can on the other hand be much 

 "acilitated by flaccidity or paralysis of the latter. 



In order to judge whether under these circumstances the 



)riskness of the " knee-jerk " varies directly with the degree of 



onus of the extensor muscles, the rapidity of onset of rigor 



iiortis, has been chosen as a guide to the degree of tonus 



existing in them before death. The experiments of Brown- 



•itquard and Hermann have proved that section of the nerve 



applying a muscle delays the time of onset of rigor mortis in 



lie muscle, even if the section is performed only shortly before 



leath. There was therefore examined the influence of section of 



he motor spinal roots on the time of onset of rigor mortis, 



.nd a delay of onset of rigor mortis was thus produced. 



I'he delay seemed as considerable as after section of the entire 



nuscular nerve. The effect of section of the sensory roots 



vas next examined, and found to be marked retardation of 



.nset of rigor ; the retardation was less if the spinal cord were 



iieviously severed in the region of the first lumbar segment. 



lif effect of placing and keeping one hind limb in the pose 



favourable for the elicitation of the "jerk" (knee flexed) 



he other limb in the position in which the jerk is restrained 



r.ucc extended) was then investigated (always after previous 



cverance of the spinal cord at the first lumbar segment). On 



Iij side on which the knee had been kept flexed the onset of 



r mortis was delayed in the extensor muscles, whereas on 



opposite side, with the knee extended rigor was delayed 



11 the flexors. It was inferred that the tonus of extensors' is 



leightened by excitation of the antagonistic set, and con- 



'cisely. 



In regard to the mutual association of action of antagon- 



•'••- muscles about other joints than the knee, it had been 



;ed in an earlier series of observations that during excita- 



of the cortical areas of the hemisphere, when isolated 



n.vtments of the pollex and hallux are being initiated, the 



novement of response obtained is often reversed by section of 



he peripheral nerve or nerves supplying those muscles which 



predominate in the movement obtained. For example, flexion 



an by section of the flexor nerve be at once converted into 



i xtension. Sometimes, however, movement in the same 



ense, although diminished in force and extent persists 



ven after cutting the nerve to the predominant group of the an - 



NO. 1232, VOL. 48] 



tagonistic muscles. This indicates that in some cases there 

 occurs, together with contraction of one group of muscles, con- 

 comitant relaxation of the antagonist. This evidence of in- 

 hibition of one set of the synergetic muscular couple during 

 co-ordinate action induced by conical excitation is in the case 

 of the digits of comparatively infrequent occurrence. In the case 

 of the eye muscles it is, on the contraiy, quite usual. 



When, the external recius muscle of one eye [e.g., of 

 the left eye) having been put out of action, the frontal cortex of 

 the right hemisphere is excited, the eyeballs if previously 

 directed to the right revert both of them to the left — i.e., the 

 excitation which evokes contraction of the right internal recius 

 evokes also relaxation of the left internal rectus. Again, when 

 the internal rectus has been put out of action — e.g., in the left 

 eye — excitation of the left frontal cortex produces, if the eyes 

 have been previously directed to the left, an immediate move- 

 ment of both eyeballs to the right, the let"t eye frequently 

 rotating beyond the median primary position. Here the same 

 excitation of the cortex which induces contraction of right 

 external rectus muscles induces synchronously a relaxation of 

 the left internal rectus muscle. These interruptions of the tonus- 

 or of the contraction of one antagonist concurrently with 

 augmentation of the contraction of its opponent are obtainable 

 not only from the sn-called " motor" region of the cortex, but 

 even more strikingly by excitation of the "visual area" of 

 occipital region of the cortex. 



Daring voluntary movements similar phenomena occur, but 

 appear less obvious than under experimental excitation of the 

 cortex. Although inhibition of contraction or tonus is appar- 

 ently so common a factor in the co-ordination of the antagon- 

 istic lateral straight muscles of the eyes, these muscles occa- 

 sionally yield good indication of synergetic contraction as well 

 as co-ordinate relaxation. The mutual association of the two 

 oblique muscles seems usually of the nature of concomitant 

 contraction, not of contraction coupled with relaxation. Oi> 

 the other hand, the muscles which close and open the palpebral 

 fissure appear to work altogether independently one of the 

 other. In their case section of the particular peripheral nerve 

 concerned in either movement is at once followed by total dis- 

 appearance of the movement, and that without reversal. 



Although the cerebral cortex exercises inhibition so readily 

 in the field of innervation of the third nerve, the dilatation of 

 the pupil evoked by excitation of that portion of the cortex 

 appeared whenever tested to be due to impulses discharged 

 vid the cervical sympathetic, and not to inhibition of the con- 

 striction exercised viA the third nerve. 



May 18. — "An Experimental Investigation of the Nerve 

 Roots which enter into the Formation of the Lumbo-Sacral 

 Plexus of jl/aira«« rhesus." By J. S. Risien Russell, M.B., 

 M.R.C.P., Assistant Physician to the Metropolitan Hospital. 



(From tlie Pattiological Labor.itory of University College, London.) 

 This formed the subject of a paper recently read before the 

 Royal Society, in which the author described one chief type of 

 plexus met with in Macaciis rhesus, the main distinguishing 

 features of which, as contrasted with the chief variation encoun- 

 tered, consisted in the fifth lumbar nerve root sending a branch 

 to the sciatic nerve trunk, and the obturator nerve taking its 

 origin from the fourth and fifth lumbar nerve roots alone, 

 whereas of the variations met with that which occurred most 

 frequently was one in which the fifth lumbar root did not send 

 a branch to the sciatic nerve, and the obturator nerve received a 

 branch from the sixth lumbar nerve root in addition to those 

 received from the fourth and fifth lumbar roots. Between 

 these two extremes all forms of variation were met with ; but 

 the upper limit of supply to the limb was always found to be 

 the third lumbar root, and the lower limit the first sacral root. 



Excitation Experiments. 



The movement which results on excitation of any given 

 nerve root with the Faradic current is a compound one made up 

 of several simple movements ; while excitation of any single 

 small bundle of nerve fibres, many of which combine to form 

 a nerve root, results in a single simple movement, and not all 

 the movements of the compound root in lessened degree. These 

 single simple movements bear an almost constant relation to 

 the nerve roots, the same movements being as a rule found in 

 any given root, and such movements always bear the same 

 relation to the spinal level. Further, each bundle of nerve 



