June 22, 1905] 



NA TURE 



189 



May 18. — " Reciprocal Innervation of Antagonistic 

 Muscles." Eighth Note. By Prof. C. S. Sherrington, 

 F.R.S. 



Exhibition of strychnine converts reflex inhibition of 

 muscles into excitation ; so also, more gradually, but just 

 as potently, does tetanus-toxin. This conversion sets in 

 before and under smaller doses of strychnine or toxin than 

 are required to produce the convulsive seizures character- 

 istic of strychnine poisoning or general tetanus. 



The conversion of inhibitory effect into excitation effect 

 by strychnine is more easily obtained in the case of some 

 nerves than of others. 



The conversion of spinal inhibition into excitation by 

 strychnine explains the simultaneous contraction of large 

 inharmonious groups of muscles in strychnine convulsions. 

 It also explains the occurrence, under a given stimulus of 

 reflex contraction, of muscles that previously do not seem, 

 under superficial examination, to be reached by the re- 

 action. These muscles are really included in the refiex 

 effect normally, but the effect on them then being 

 inhibition, it passes unnoticed, unless special means are 

 adopted for seeing it. Thus, in the ordinary " flexion 

 reflex," initiated, say, from the right foot, the flexion of 

 the homonymous knee is easily seen to be due to contrac- 

 tion of its flexor muscles, also the concomitant extension 

 of the crossed knee is easily seen to be due to contraction 

 of its extensor muscles. But it requires special prepar- 

 ations to detect that, with the contraction of the right 

 knee-flexors, there goes reflex inhibition of the right 

 extensor, and that, with the contraction of the left knee- 

 extensor, there goes reflex inhibition of the left knee- 

 flexors. This being so, when under strychnine, the reflex 

 is suddenly changed in character, both flexors and extensors 

 being in both legs thrown into contraction together, it 

 appears to an observer, unaware of the previous inhibitions, 

 that, under the strychnine, the reflex action reached 

 muscles which it did not reach before, e.^. right knee- 

 extensor and left knee-flexor. Hence arises the hypothesis 

 that the alkaloid breaks down a supposed spinal " resist- 

 ance," previously intervening between the afferent nerves 

 and various motor spinal cells ordinarily inaccessible to 

 them. Strychnine does lower the threshold stimulus for 

 spinal reflexes at one stage of its action ; but the central 

 fact of strychnine effect appears to the author that it 

 destroys spinal taxis for the skeletal musculature by up- 

 setting the fundamental coordination of reciprocal inner- 

 vation. It upsets reciprocal innervation because it trans- 

 forms inhibition into excitation. 



On the view advanced in these notes previously that 

 the cortex of the brain exercises reciprocal innervation of 

 antagonistic muscles, strychnine and tetanus-to.xin should 

 transform the functional topography of the " motor " 

 cortex. This on examination proves to be the case. 



Strychnine and tetanus-toxin change cortical flexion of 

 leg and arm into extension. Reflex " opening " of the jaw 

 is in the decerebrate animal converted into retlex closure by 

 tetanus-toxin and by strychnine, the inhibition of the pre- 

 dominantly powerful closing muscles being converted into 

 excitation of them. 



Similarly, when the " face-area " of the monkey's cortex 

 is tested by faradisation after exhibition of strychnine or 

 tetanus-toxin, the points of surface that, prior to the drug, 

 yield regularly the free opening of the jaw, yield strong 

 closure of the jaw instead. Closure of the jaw is, com- 

 paratively, an infrequent movement to obtain from the 

 cortex of the monkey. On the other hand, opening of the 

 jaw is always readily and regularly elicitable from a large 

 field of the "face-area." Under tetanus toxin and 

 strychnine the whole of this area not only ceases to yield 

 opening of the jaws, either maintained or rhythmic, but 

 yields closing of them instead. 



The foregoing observations give an insight into the 

 essential nature of the condition brought about by tetanus 

 and by strychnine poisoning. These disorders work havoc 

 with the coordinating mechanisms of the central nervous 

 system, because, in regard to certain great groups of 

 musculature, they change the reciprocal inhibitions, 

 normally assured by the central nervous mechanisms, into 

 excitations. The sufferer is subjected to a disorder of 

 coordination which, though not necessarily of itself accom- 



NO. i860, VOL. 72] 



panied by physical pain, inflicts on the mind, which still 

 remains clear, a torture inexpressibly distressing. Each 

 attempt to execute certain muscular acts of vital import- 

 ance, such as the taking of food, is defeated because e.xactly 

 the opposite act to that intended results from the attempt. 

 The endeavour to open the jaw to take food or drink 

 induces closure of the jaw, because the normal inhibition 

 of the stronger set of muscles — the closing muscles — is by 

 the agent converted into excitation of them. Moreover, the 

 various reflex arcs that cause inhibition of these muscles 

 not only cause excitation of them instead, but are, 

 periodically or more or less constantly, in a state of hyper- 

 excitement, and yet attempt on the part of the sufferer to 

 restrain, to inhibit, their reflex reaction, instead of re- 

 laxing them, only heightens their excitation further, and 

 thus exacerbates a rigidity or a convulsion already in 

 progress. 



" The Structure and Function of Nerve Fibres. — Pre- 

 liminary Communication." By Prof. J. S. Macdonald. 



Communicated by Prof. C. S. Sherrington, F.R.S. 



In contradiction to certain conclusions ' arrived at by 

 the author as a consequence of his experimental observ- 

 ation of the " injury current " of nerve, it has recently 

 been denied " that inorganic salts occur in any appreciable 

 quantity within the internal structure of the nerve-fibre. 

 This conclusion has been formed as the result of observ- 

 ations made with the use of a reagent — cobalt nitrite — 

 which precipitates potassium salts in a manner open to 

 investigation with the microscope. It has been shown that 

 the reagent does not give rise to precipitates at every 

 point in the length of the nerve-fibre, but only at certain 

 points of infrequent occurrence. The author has checked 

 this statement, also using microscopical methods, and con- 

 firms it. He draws, however, an entirely different con- 

 clusion from these observations, since he has further 

 observed that these points of infrequent occurrence are 

 points at which the axis-cylinder has been injured in the 

 course of preparation. He concludes that potassium salts 

 are really present in very considerable quantity uniformly 

 distributed along the axis-cylinder, but that they appear 

 in a state of simple solution only at injured points. 



The author directs attention to the possible general im- 

 portance acquired by this observation, when account is 

 taken of the parallelism between injury and "excitation." 

 The sudden appearance of inorganic salts (electrolytes) in 

 a state of simple aqueous solution at an excited point 

 means a transitory increase in local osmotic pressure, new 

 processes of diffusion, and disturbances of electrical 

 potential. In this he sees a sufficient explanation of nerve- 

 conduction. In the case of muscle, also, the influence of 

 similar phenomena is considered, and a possible relation 

 between such an increase in local osmotic pressure and 

 "contraction." He also refers to the possibility of the 

 influence of this factor in the conditions determining the 

 flow of water in plant structures. 



June 8. — " The Perturbations of the Bielid Meteors." 

 By Dr. A. M. W. Downin^i F.R.S. 



As the general result of the calculations described in this 

 paper, it appears that the most probable date for the centre 

 of a shower of Bielid meteors this year is November i8, 

 loh., G.M.T. If there be a shower at that date, it will 

 indicate that the meteor stream is, in this part, of sufficient 

 length to occupy at least thirty-three days (October i6 to 

 November i8) in passing a definite point in its orbit — or 

 that there is another swarm following the main swarm at 

 this interval — and is also of sufficient extent in the direc- 

 tion sun-earth to allow of some of the meteors encounter- 

 ing the earth, although the centre of the stream is more 

 than 1,000,000 miles outside the earth's orbit at the time. 



" Chitin in the Carapace of Pterygotus osiliensis, from 

 the Silurian of Oesel." By Dr. Otto Rosenheim. Com- 

 municated by Prof. W. D. Halliburton, F.R.S. 



Fragments of the carapace of certain fossil Eurypterids 

 found in Oesel in rocks of Silurian age, from specimens 



1 J. S. Macdonald, " Thompson- Yates Laboratory Reports," vol. iv., 

 part ii., pp. 213-348, 1902 ; Proc. Roy. Sac, vol. Ixvii., pp. 315-324 ; id/ci., 

 pp. 325-328 ; Proc. Physiol. Soc, December 17, 1904 ; ibid.^ March iS, 

 1905. 



- A. B. MAC3.\\\xm, Journal of Physiology^ vol. xxxii. p. i. 



