712 NERVOUS SYSTEM. (NERVOUS CENTRES. ABNORMAL ANATOMY.) 



columns of the cord, partly through the deep 

 fibres of its great commissure, the pons Varolii, 

 which interlace freely with the fibres of the 

 anterior pyramids, vesicular matter being in- 

 terposed, and partly through those portions of 

 the restiform bodies which penetrate the antero- 

 lateral columns of the spinal cord. It asso- 

 ciates and harmonizes the movements of the 

 trunk, and especially those of the lower ex- 

 tremities, for locomotion, through those por- 

 tions of the restiform bodies which are con- 

 tinued with the posterior columns of the cord. 



The crossed influence of deep lesion of either 

 hemisphere of the cerebellum is difficult to 

 explain in the absence of any proved decus- 

 sation of the restiform bodies. The connection 

 of the deep fibres of the pons, however, with 

 the anterior pyramids in the mesocephale does 

 afford some explanation. If, for instance, the 

 left cerebellar hemisphere be the seat of lesion, 

 these fibres will be affected, and they may in- 

 fluence the fibres of the left pyramid, which 

 again will affect the right half of the cord and 

 the right side of the body. Those fibres of 

 the restiform bodies which incorporate them- 

 selves with the antero-lateral columns, are 

 doubtless too few to produce much influence. 



ABNORMAL ANATOMY OF NERVES AND NER- 

 VOUS CENTRES. The great space already occu- 

 pied by this article obliges me to compress into 

 as small a compass as possible the observations 

 which I propose to make under this head. 



An interesting preliminary question is to de- 

 termine to what extent nervous matter is capa- 

 ble of being regenerated, when any solution of 

 its continuity may have occurred. In nerve it 

 has long been proved that such regeneration is 

 capable of taking place. If the nerve be 

 simply divided, without loss of substance, 

 union may take place immediately ; but if a 

 piece of it have been cut away, a considerable 

 period must elapse before its complete restora- 

 tion. This was satisfactorily proved by Dr. 

 Haighton's* experiments, in which he found 

 that the function of the inferior laryngeal nerve 

 in dogs was restored six months after division 

 of the vagus, but with altered tones. Tiede- 

 mann divided in a dog the nerves of the fore- 

 foot and leg, and at the expiration of eight 

 months observed that sensation and motion re- 

 turned ; after twenty-one months the sensi- 

 tive power had increased considerably, and 

 at length the dog regained the complete use of 

 his foot. Schwann divided both sciatic nerves 

 of a frog, in the middle of both thighs : imme- 

 diately after the operation the frog's movements 

 were very imperfect; after a month it had 

 gained some power; but in three months it 

 leaped as well as if no division had taken place. 

 The sensibility of the foot, which was destroyed 

 by the section, became nearly entirely restored; 

 and irritation of the nerve with a needle above 

 the cicatrix produced strong contractions in the 

 muscles supplied from the nerve below the 

 wound. On examination with the microscope, 

 Schwann found that the cicatrix consisted of 

 true nerve fibres disposed in their usual way.f 



* Phil. Trans. 1795. 



t Quoted in Muller's Physiology. 



Miiller mentions the interesting fact of the 

 return of some degree of sensation in the flaps 

 of skin used for the Taliacotian operation for a 

 new nose, as an argument in favour of the re- 

 production of nerves. Dieffenbach, however, 

 who has had so much experience in these ope- 

 rations, states that the return of sensibility is 

 only very imperfect, which is to be expected, 

 since the divided extremities of the same fibres 

 cannot re-join, except in very small number. 



The evidence of restoration of function in 

 divided nerves in the human subject is imper- 

 fect, although not opposed to what has been 

 above stated. Gruithuisen's observations on 

 the consequences of an accidental division of 

 the dorsal nerve of the thumb in his own per- 

 son are sufficiently conclusive. Eight months 

 after the division, although the sensation had 

 returned, it was so imperfect that the mind 

 could form no conception of the precise point 

 stimulated, as if the isolation of the fibres so 

 necessary to exact sensation had been de- 

 stroyed in the cicatrix, or as if the fibres of the 

 peripheral portion of the nerve had not united 

 with the corresponding ones in its central por- 

 tion. Mr. Earle relates a case in which a part 

 of the ulnar nerve was cut out ; at the end of 

 four years the little finger was useless, and the 

 sensations very imperfect. 



Indeed there is much difficulty in drawing 

 conclusions from the restoration or non-restora- 

 tion of function after division of nerves, for no 

 artificial disposition of the cut extremities will 

 insure the correspond ing fibres meeting. A sen- 

 sitive fibre may be joined to a motor, and thus 

 the office of both would be neutralised ; or dif- 

 ferent sensitive fibres might unite, from which 

 doubtless some confusion as to the nature and 

 position of the impression would ensue. 



The microscopic examinations of Seinruch, 

 Hermann, Nasse, and Klencke have rendered it 

 certain that true nerve-fibres are reproduced in 

 the cicatrix of a divided nerve. Nasse states that 

 they are smaller than the natural size; and 

 he has likewise pointed out an interesting 

 fact, in the decrease of size of the fibres of the 

 peripheral segment of the nerve as compared 

 with those of the central segment, showing that 

 a certain degree of atrophy takes place in that 

 portion of the nerve, even after it has been se- 

 parated for a short period from its connection 

 witli the nervous centre. This author never 

 saw sensation and motion return, although he 

 kept the animals for three quarters of a year. 

 Perhaps this was owing to his having removed 

 large portions of the nerves he operated upon. 



With respect to the reproduction of solutions 

 of continuity in the nervous centres, what little 

 is known must be viewed as unfavourable to the 

 supposition that perfect restoration of the lost 

 parts takes place. If the brain or spinal cord 

 be wounded, union will take place; but it does 

 not appear from Arnemanu's observations nor 

 from Flourens's that the uniting substance is 

 true nervous matter. Further researches are 

 much needed upon this interesting subject. 



Abnormal anatomy of the spinal con/ and its 

 membranes. The membranes of the spinal cord 

 are liable to those morbid changes which com- 



