182 ORIGINAL ARTICLES. 



the connexion of the fibres with muscles in the one case, and with the 

 centre of sensation in the other."* The principle here laid down is 

 irreversible ; bat it is an error to suppose that only one of the nerves is 

 in connexion with the centre of sensation. I pointed out the fact, 

 which had been universally disregarded, that the anterior (motor) roots 

 were quite as unmistakeably in anatomical connexion with the gan- 

 glionic substance of the spinal chord, as the posterior roots were ; 

 and the conclusion seemed irresistible, that if one nerve in connexion 

 with a centre will stimulate the activity of that centre, another nerve 

 precisely analogous in structure, and endowed with an analogous pro- 

 perty (propagating the same nervous force), if also in connexion with 

 that centre, must also stimulate its activity. Modern microscopic re- 

 searches have rendered the direct connexion of the anterior roots with 

 the ganglionic substance, a fact beyond dispute. To resist the con- 

 clusion I have drawn, it. will be necessary to prove : 1st. That the 

 ganglionic substance with which the anterior roots is connected has not 

 the same property as the ganglionic substance of the posterior roots ; 

 or, 2nd. That nerves are only capable of stimulating in one direction. 

 But it has been proved by Schiff that there is no difference between the 

 properties of the anterior and posterior horus. And it has also been 

 proved that nerves conduct in both ways. 



If, therefore, Sensibility is the property of Nerve-centres awakened 

 by the stimulus of JN"eurility — if both nerves are in direct anatomical 

 connexion with their centres — and if there be not two different kinds of 

 ISTeurility, acting in very different ways upon the centre — there is no al- 

 ternative but to accept the conclusion that both nerves have a sensory 

 function. 



In vindicating the essential similarity of the two sets of nerves, we 

 are not overlooking their specific diversity. The functions of various 

 nerves, that is to say, the uses they serve in the mechanism, depend 

 upon their anatomical connexions. A nerve that is not distributed to a 

 muscle cannot be expected to have a motor function ; a nerve that is not 

 distributed to a gland cannot be expected to have a secretory function ; 

 a nerve that is not distributed to an organ of sense cannot be expected 

 to have a function of special Sensation. 



Bell's discovery that the anterior roots ministered to motion, and the 

 posterior to sensation, may be interpreted thus : the anterior nerves are 

 muscle-nerves, the posterior are skin-nerves. My critic in the British 

 and Foreign demurs to this. " It is known to every anatomist," he says, 

 " that it is a pure assumption on the part of Mr. Lewes to assert that the 

 fibres of the anterior roots are distributed fexclusively to the muscles, 

 and those of the posterior roots exclusively to the skin. How, we would 

 ask, is it possible anatomically to separate the fibres of the anterior and 

 the posterior roots in any nerve of mixed endowments ? and on what 

 basis, save that of physiological experiment, can any positive statement 



Todd, Physiol, of Nervous System, in Cyclopaed. of Anat. and Phys. 



