142 



NA TURE 



[June 8, 1893 



fibres representing a single simple movement in a nerve root 

 remains distinct in its course to the muscle or muscles, pro- 

 ducing such a movement without inosculating with other motor 

 nerve fibres. 



Muscles diametrically opposed in their action are represented 

 in the same nerve root, but in different degrees, and when a 

 certain group of muscles predominate in their action in one 

 root they as a rule predominate in that root. In those instances 

 in which the opposed movements are represented in three con- 

 secutive nerve roots the middle root of the series is that in which 

 both movements are represented, while the root above contains 

 the one movement, and that below contains the other. 



The movements of flexion and extension are found to alter- 

 nate in their representation from above down, flexion being at 

 a higher level than extension in the highest segment of the 

 limb, while extension is above flexion in the next, and so on. 



A muscle is usually represented in two nerve roots, and to an 

 unequal extent in these ; and when variations occur, it is, as a 

 rule, that one of the nerve roots in which the muscle is repre- 

 sented is different, rather than that it is represented in more 

 nerve roots. When the same muscle is represented in two 

 nerve roots the muscle fibres innervated by one root are not 

 innervated by the other, so that only part of the muscle con- 

 tracts when a single root is excited. 



Ablation Experiments. 



Division of any given nerve root produces paresis of the group 

 of muscles supplied by it, which paresis is temporary, nearly all 

 of it being recovered from. The amount of paresis or paralysis 

 produced is proportional to the number of nerve roots divided ; 

 and this again varies according to whether the roots divided are 

 consecutive or alternate ones, the effect being much greater in 

 the former than in the latter case. Such division of one or 

 more nerve roots does not result in incoordination of the 

 remaining muscular combinations represented in other nerve 

 roots ; the remaining movements are merely more feeble. 



Exclusion of a certain Root or Roots during an Epileptic 

 Convulsion in the Limb. 



Division of one or more nerve roots produces alteration of 

 the position of a limb during an epileptic convulsion, which 

 altered position depends on the muscular combinations that have 

 been thus thrown out of action. And the effect is identical 

 when the root or roots are divided at the time when the convul- 

 sions are evoked, and when they have been divided some weeks 

 previously. No incoordination is produced in the remaining 

 muscular combinations ; and there is no evidence of overflow 

 of the impulses which ought to travel down the divided root 

 into other channels through the spinal centres, so as to reach 

 the muscles by new paths. 



" A Further Minute Analysis by Electric Stimulation of the 

 so-called Motor Region (Facial Area) of the Cortex Cerebri 

 in (he Monkey {Afacacus sinicus)." By Charles E. Beevor, 

 M.D., F.R.C.P., and Victor Horsley, M.B., F.R.C.S., 

 F.R.S. 1 



(From the Laboratory of the Brown Institution, and from the Pathological 

 Department of University College, London.) 



In the paper of which this is an abstract the authors have com- 

 pleted the minute analysis of the movements elicited by excitation 

 of the excitable (so-called motor) region of the cortex cerebri in 

 the Bonnet Monkey {Macacus sinicus). The portions hitherto 

 examined having been those in which the movements of the limbs 

 were represented, the facial area was chosen for the present 

 research. After an historical introduction and a description of 

 the anatomy of the region investigated, the method of notation 

 and record of results is discussed. 



Considering that in this part of the cortex cerebri there is 

 well-defined representation of movements of both sides of the 

 body, the question of bilaterality of representation is raised, and 

 attention directed to its importance. The analysis of the results 

 obtained show that there existed precise localisation for the 

 movements of the individual portions of the face, even to that of 

 half the lower lip. 



The specialisation of the movements of the tongue was 



' The expenses of this research were defrayed principajly by a grant from 

 ihe Government Grant Fund of the Royal Society, and in part by a grant 

 from the .Scientific Grants Committee of the British Medical Association. 



rendered easy of examination by employing the operative device 

 of dividing the tongue in the middle line. This shed unexpected 

 light on the representation of the movements of this organ. 



Movements of the pharynx were made the subject of 

 observation, and some degree of unilaterality was discovered in 

 the movements of the soft palate. 



Finally, attention is drawn to the fact that the marches of 

 movements in succession are in this region very inconstant and 

 difficult to arrange. 



"On the presence of Urea in the Blood of Birds, and its 

 bearing upon the Formation of Uric Acid in the Animal 

 Body." By Sir Alfred Garrod, M.D., F.R.S. 



The author gives in his paper a resume of the opinions held 

 with regard to the formation of uric acid in the animal economy 

 during the last half century, and then announces his discovery of 

 the presence of urea in the blood of birds in quantities practi- 

 cally the same as that which is present in the mammalian blood ; 

 by which discovery the views hitherto held as to the formation 

 of uric acid are necessarily modified. Having afterwards shown 

 that the kidneys have no power of removing uric acid from 

 blood, and referred to other physiological points in connection 

 with uric acid and urea, he sums up most of his views in the fol- 

 lowing propositions : — 



First. That in mammalia and other urea-excreting animals 

 the metabolism of the nitrogenised tissues results in the forma- 

 tion of urea as an ultimate product ; that an appreciable and 

 measurable amount of this substance is always found in their 

 blood, and is constantly being excreted by the kidneys ; and, 

 further, that any cause leading to the decrease of this excretion 

 produces an augmentation of the urea in the blood. 



Second. That in birds, and other uricacid-excreting animals, 

 the metabolism of the nitrogenised tissues is exactly the same as 

 in mammals, and that urea is the ultimate product of this 

 metabolism ; that urea is always present in their blood, in 

 quantities not less than in mammalian blood, and that the urate 

 of ammonium is a subsequent product of the union of urea with 

 some other principle or principles, glycine probably being one 

 of them. Consequently, it is not necessary that uric acid should 

 be present in the blood of uric-acid-excreting animals : in health, 

 in fact, it is not detectible. When it is present, its presence is 

 a result of its having been absorbed after formation in the 

 kidneys or elsewhere. 



Geological Society, May 24. — W. H. Hudleston, F.R.S., 

 President, in the chair. — The following communications were 

 read : — Notes on Dartmoor, by Lieut. -General C. A. McMahon. 

 The author alluded to a memoir on the British Culm Measures 

 recently published by Mr. Ussher, in which the view is advanced 

 that the granite of Dartmoor resulted from the metamorphism 

 of pre-existing rocks which had in a rigid state offered obstruc- 

 tion to a long sustained N. and S. squeeze, and that their fusion 

 and consequent consolidation were effected in situ. The author 

 gave some of the results of a visit to the western borders of 

 Dartmoor. He detailed some examples of eruptive granite- 

 veins intruding into Culm beds in the immediate vicinity of the 

 main mass of granite. The latter, in the locality described, is 

 porphyritic down to its boundary, and the veins are also por- 

 phyritic. All the circumstances lead to the belief that these 

 veins are real apophyses from the main mass, and that the view 

 adopted by De la Beche regarding the origin of the Dartmoor 

 granite is the true one. After alluding to some features in the 

 Meldon granite-dyke not before noted, some detailed observa- 

 tions in the bed of the River Tavey were given, and an explana- 

 tion i.ffered of the way in which the fine-grained marginal variety 

 of the granite, seen in that locality, has been produced. The 

 improbability that a tremendous squeeze sufficient to fuse 225 

 square miles of a pre-Devonian rock into granite while the Ctilro 

 Measures outside the zone of marginal contact-meiamorphisro 

 are left almost untouched was commented upon, and finally, the 

 author alluded to the often-observed pseudo-stratification of the 

 Dartmoor granite, and urged that the cause of this is not the ope 

 suggested by De la Beche, but that it is due to sub-aerial 

 agencies. The reading of the paper was followed by a discussion 

 in which the President, Mr. Watts, Mr. Teall, Mr. Ruiley, Prof. 

 Bonney, and Prof. Hull took part. General McMahon briefly 

 replied. — On some recent borings through the lower Cretaceous 

 strata in East Lincolnshire, by A. J. Jukes-Browne. The bor- 

 ings described in this paper are at'Alford, Willoughby and 

 Skegness, and disclose the existence of an unsuspected anti- 

 clinal axis, bringing up Lower Cretaceous rocks beneath the 



NO. 1232, VOL. 48] 



