THE SPINAL CORD. 667 



be the case, it does not seem at all improbable that there should be a difference 

 in different tribes of animals, as to the proportion of fibres which have their 

 centres in the Spinal cord and in the Sensorial centres respectively; for in 

 those whose ordinary movements of progression, &c., are independent of sensa- 

 tion, being performed through the reflex action of the spinal cord, it might 

 be expected that the chief connection of the spinal nerves should be with its own 

 ganglionic substance, and that the bulk of the fibrous columns should be com- 

 posed of eommissural fibres resembling those which intervene between the sepa- 

 rate portions of the ganglionic tract of the ventral cord of Articulata ; whilst in 

 like manner it might be anticipated that in Man, so large a part of whose move- 

 ments are performed in obedience to a mental stimulus and under the guidance 

 of sensation, the longitudinal strands should be chiefly composed of fibres that 

 directly connect the sensorial centres with the roots of the spinal nerves. Such 

 a difference would appear, from the comparative researches of MM. Volkmann 

 and Kolliker, to exist between the structure of the Spinal cord of the Horse and 

 that of Man. 



702. Of the three doctrines previously stated, then, the third appears to be 

 most in conformity with the analogy of the lower animals; whilst it is fairly 

 justified by all that is certainly known of the anatomical structure of the Spinal 

 Cord in Man. When originally advanced by Mr. Grainger, 1 its novelty chiefly 

 consisted in the idea that any of the root-fibres of the spinal nerves have their 

 central termination in the Spinal Cord; and no doubt was at that time entertained 

 by Anatomists or Physiologists, that the Encephalic fibres pass onwards continu- 

 ously to the peripheral surface of the Cerebrum, and directly minister to volun- 

 tary movement as well as to sensation. Consequently, Mr. Grainger's view of 

 the constitution of the Spinal Cord was considered by many Physiologists (among 

 whom the Author is not ashamed to have himself ranked) as affording the needed 

 structural confirmation to Dr. Marshall Hall's hypothesis of a system of nerve- 

 fibres ministering to the reflex action of the Cord, physiologically distinct from 

 those which are subservient to sensation and voluntary movement. But when 

 that distinction is made between the several Encephalic centres which there now 

 appears ground for relying on, those fibres which connect them with the Spinal 

 nerves are no longer to be accounted Cerebral, nor to be regarded as ministering 

 to volition ; but, on the other hand, are to be considered as merely Sensorial, 

 and as belonging, no less than the fibres which link together the several seg- 

 ments of the Spinal Cord itself, to the " automatic apparatus" ( 677). Thus 

 the view here advocated has a close physiological resemblance to the doctrine of 

 Messrs. Todd and Bowman, Volkmann, &c. ; whilst it is in full conformity with 

 the anatomical facts supplied by Prof. Kolliker; for, whilst it recognizes the 

 white columns of the Spinal Cord as chiefly composed of fibres which form a 

 continuous connection between the nerve-roots and certain Encephalic centres, 

 it regards these fibres as really of the same order with those which are generally 

 admitted to pass from the nerves of one segment of the Spinal Cord to other 

 segments above and below it, the only difference being that they extend them- 

 selves to its cranial segments : and it considers the entire " automatic apparatus" 

 as receiving all the terminations of the nerves, so that all impressions upon the 

 afferent nerves first operate upon it (affecting the consciousness, or not, accord- 

 ing as they reach the sensory ganglia, or are arrested in their progress thither); 

 and all motor impulses, whether simply reflex, or orginating in emotional or 

 volitional excitement, are issued from it through the nerve-trunks to the mus- 

 cles. 



703. In considering the functions of the Spinal Cord, we have to regard it 

 under two aspects; in the first place, as a conductor of nervous force between 



1 "Observations on the Structure and Functions of the Spinal Cord," 1837. 



