274 FUNCTIONS OF THE NERVOUS SYSTEM. 



destroyed by injury or disease, without any corresponding loss of the func- 

 tion attributed to it.* Such cases have kept alive, in the minds of many emi- 

 nent practical men, a considerable distrust of the accuracy of Sir C. Bell's 

 conclusions. We have seen that, in regard to the roots of the nerves, his 

 first statements have been confirmed, and rendered more precise, by subse- 

 quent researches ; but it is not so in regard to the functions of the anterior 

 and posterior divisions of the Spinal Cord. Bellingeri was led, by experi- 

 ments on the spinal cord, to the conclusion, that the anterior roots of the 

 nerves were for the flexion of the various articulations, and the posterior for 

 their extension. He also was wrong, in extending an inference, founded on 

 experiments on the Cord, to the roots of the nerves. The recent experiments 

 of Valentin, whilst they fully confirm Sir C. Bell's determination of the func- 

 tions of the roots of the nerves, coincide, to no small degree, with Bellingeri's 

 opinion, in regard to the offices of the anterior and posterior divisions of the 

 Cord. He obtained reason to believe that, in the Frog, neither the superior 

 nor inferior strand of the cord (posterior and anterior columns in Man) solely 

 possesses motor functions ; but he found that, when the former were irritated, 

 sensations predominated ; and when the latter, motions were chiefly excited. 

 He further states that, if the superior strand (posterior column) be irritated 

 at the point at which the nerves of either extremity are given ofl', that ex- 

 tremity is extended ; and that if the inferior strand (anterior column) be irri- 

 tated, the extremity is flexed. At their entrance into the spinal cord, there- 

 fore, it would appear that the motor fibres of the extensors pass towards the 

 superior stratum (posterior column in Man), whilst those of the flexors are 

 continuous with the inferior stratum (inferior column) ; their course being 

 more altered, however, when they are examined far from the point of issue. 

 This doctrine was confirmed by experiments on Mammalia ; and is borne out 

 (according to Valentin) by pathological phenomena observed in Man. Accord- 

 ing to this eminent physiologist, also, relaxation of the sphincters is analogous 

 to the extended state of the extremities ; and he has noticed a manifest relaxa- 

 tion of the sphincter ani in the frog, when the superior part of the spinal 

 cord was irritated, so as to produce extension of the limbs. These state- 

 ments are entitled to considerable weight, on account of the quarter from 

 which they come ; but they are not, perhaps, to be received altogether with- 

 out hesitation, until confirmed by other physiologists, especially whilst the 

 phenomena of reflex action are still so imperfectly known. For it is quite 

 possible that, whilst stimulation of the anterior part of the cord may excite 

 direct motions of flexion, in preference to those of extension, the movements 

 of extension produced by stimulating the posterior column may be of a reflex 

 character. 



350. There is no reason to believe, that the functions of the Spinal Cord 

 are essentially different along its whole length. Everywhere it appears to 

 consist of a ganglionic centre, supplying nerves to its particular segment ; 

 and of connecting fibres, by which the nerves proceeding from any one divi- 

 sion are brought into relation with distant portions of the organ, and with the 

 large ganglionic masses at its anterior extremity. In this respect, then, it 

 corresponds precisely with the double nervous cord of the Articulata ; the 

 only prominent difference between the two being, that in the former the gan- 

 glionic matter is continuous from one extremity of the organ to the other; 

 whilst in the latter it is interrupted at intervals ; and in the Mollusca, the 

 centres are still further separated from each other. The connection of the 



* Sec especially a case recorded by Dr. Webster (Medico-Chinirgical Transactions, vol. 

 xxvi.), in which there was complete destruction of the posterior columns in the lower p;irt 

 of the cervical region ; which was not attended with loss of sensibility in the parts below, 

 but, on the contrary, with loss of power of voluntary motion. 



